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| author | Dongsheng Song <dongsheng.song@gmail.com> |
|---|---|
| date | Mon Mar 30 17:36:57 2009 +0800 (2009-03-30) |
| parents | 1c13ed2130a7 |
| children | b338f5490029 |
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1 <!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
3 <chapter id="cha:collab">
4 <?dbhtml filename="collaborating-with-other-people.html"?>
5 <title>Collaborating with other people</title>
7 <para id="x_44a">As a completely decentralised tool, Mercurial doesn't impose
8 any policy on how people ought to work with each other. However,
9 if you're new to distributed revision control, it helps to have
10 some tools and examples in mind when you're thinking about
11 possible workflow models.</para>
13 <sect1>
14 <title>Mercurial's web interface</title>
16 <para id="x_44b">Mercurial has a powerful web interface that provides several
17 useful capabilities.</para>
19 <para id="x_44c">For interactive use, the web interface lets you browse a
20 single repository or a collection of repositories. You can view
21 the history of a repository, examine each change (comments and
22 diffs), and view the contents of each directory and file.</para>
24 <para id="x_44d">Also for human consumption, the web interface provides an
25 RSS feed of the changes in a repository. This lets you
26 <quote>subscribe</quote> to a repository using your favourite
27 feed reader, and be automatically notified of activity in that
28 repository as soon as it happens. I find this capability much
29 more convenient than the model of subscribing to a mailing list
30 to which notifications are sent, as it requires no additional
31 configuration on the part of whoever is serving the
32 repository.</para>
34 <para id="x_44e">The web interface also lets remote users clone a repository,
35 pull changes from it, and (when the server is configured to
36 permit it) push changes back to it. Mercurial's HTTP tunneling
37 protocol aggressively compresses data, so that it works
38 efficiently even over low-bandwidth network connections.</para>
40 <para id="x_44f">The easiest way to get started with the web interface is to
41 use your web browser to visit an existing repository, such as
42 the master Mercurial repository at <ulink
43 url="http://www.selenic.com/repo/hg?style=gitweb">http://www.selenic.com/repo/hg?style=gitweb</ulink>.</para>
45 <para id="x_450">If you're interested in providing a web interface
46 to your own repositories, Mercurial provides two ways to do
47 this. The first is using the <command role="hg-cmd">hg
48 serve</command> command, which is best suited to short-term
49 <quote>lightweight</quote> serving. See <xref
50 linkend="sec:collab:serve"/> below for details of how to use
51 this command. If you have a long-lived repository that you'd
52 like to make permanently available, Mercurial has built-in
53 support for the CGI (Common Gateway Interface) standard, which
54 all common web servers support. See <xref
55 linkend="sec:collab:cgi"/> for details of CGI
56 configuration.</para>
58 </sect1>
59 <sect1>
60 <title>Collaboration models</title>
62 <para id="x_451">With a suitably flexible tool, making decisions about
63 workflow is much more of a social engineering challenge than a
64 technical one. Mercurial imposes few limitations on how you can
65 structure the flow of work in a project, so it's up to you and
66 your group to set up and live with a model that matches your own
67 particular needs.</para>
69 <sect2>
70 <title>Factors to keep in mind</title>
72 <para id="x_452">The most important aspect of any model that you must keep
73 in mind is how well it matches the needs and capabilities of
74 the people who will be using it. This might seem
75 self-evident; even so, you still can't afford to forget it for
76 a moment.</para>
78 <para id="x_453">I once put together a workflow model that seemed to make
79 perfect sense to me, but that caused a considerable amount of
80 consternation and strife within my development team. In spite
81 of my attempts to explain why we needed a complex set of
82 branches, and how changes ought to flow between them, a few
83 team members revolted. Even though they were smart people,
84 they didn't want to pay attention to the constraints we were
85 operating under, or face the consequences of those constraints
86 in the details of the model that I was advocating.</para>
88 <para id="x_454">Don't sweep foreseeable social or technical problems under
89 the rug. Whatever scheme you put into effect, you should plan
90 for mistakes and problem scenarios. Consider adding automated
91 machinery to prevent, or quickly recover from, trouble that
92 you can anticipate. As an example, if you intend to have a
93 branch with not-for-release changes in it, you'd do well to
94 think early about the possibility that someone might
95 accidentally merge those changes into a release branch. You
96 could avoid this particular problem by writing a hook that
97 prevents changes from being merged from an inappropriate
98 branch.</para>
100 </sect2>
101 <sect2>
102 <title>Informal anarchy</title>
104 <para id="x_455">I wouldn't suggest an <quote>anything goes</quote>
105 approach as something sustainable, but it's a model that's
106 easy to grasp, and it works perfectly well in a few unusual
107 situations.</para>
109 <para id="x_456">As one example, many projects have a loose-knit group of
110 collaborators who rarely physically meet each other. Some
111 groups like to overcome the isolation of working at a distance
112 by organising occasional <quote>sprints</quote>. In a sprint,
113 a number of people get together in a single location (a
114 company's conference room, a hotel meeting room, that kind of
115 place) and spend several days more or less locked in there,
116 hacking intensely on a handful of projects.</para>
118 <para id="x_457">A sprint is the perfect place to use the
119 <command role="hg-cmd">hg serve</command> command, since
120 <command role="hg-cmd">hg serve</command> does not require any
121 fancy server infrastructure. You can get started with
122 <command role="hg-cmd">hg serve</command> in moments, by
123 reading <xref linkend="sec:collab:serve"/> below. Then simply
124 tell the person next to you that you're running a server, send
125 the URL to them in an instant message, and you immediately
126 have a quick-turnaround way to work together. They can type
127 your URL into their web browser and quickly review your
128 changes; or they can pull a bugfix from you and verify it; or
129 they can clone a branch containing a new feature and try it
130 out.</para>
132 <para id="x_458">The charm, and the problem, with doing things in an ad hoc
133 fashion like this is that only people who know about your
134 changes, and where they are, can see them. Such an informal
135 approach simply doesn't scale beyond a handful people, because
136 each individual needs to know about $n$ different repositories
137 to pull from.</para>
139 </sect2>
140 <sect2>
141 <title>A single central repository</title>
143 <para id="x_459">For smaller projects migrating from a centralised revision
144 control tool, perhaps the easiest way to get started is to
145 have changes flow through a single shared central repository.
146 This is also the most common <quote>building block</quote> for
147 more ambitious workflow schemes.</para>
149 <para id="x_45a">Contributors start by cloning a copy of this repository.
150 They can pull changes from it whenever they need to, and some
151 (perhaps all) developers have permission to push a change back
152 when they're ready for other people to see it.</para>
154 <para id="x_45b">Under this model, it can still often make sense for people
155 to pull changes directly from each other, without going
156 through the central repository. Consider a case in which I
157 have a tentative bug fix, but I am worried that if I were to
158 publish it to the central repository, it might subsequently
159 break everyone else's trees as they pull it. To reduce the
160 potential for damage, I can ask you to clone my repository
161 into a temporary repository of your own and test it. This
162 lets us put off publishing the potentially unsafe change until
163 it has had a little testing.</para>
165 <para id="x_45c">In this kind of scenario, people usually use
166 the <command>ssh</command> protocol to securely push changes
167 to the central repository, as documented in <xref
168 linkend="sec:collab:ssh"/>. It's also usual to publish a
169 read-only copy of the repository over HTTP using CGI, as in
170 <xref linkend="sec:collab:cgi"/>. Publishing
171 over HTTP satisfies the needs of people who don't have push
172 access, and those who want to use web browsers to browse the
173 repository's history.</para>
175 </sect2>
176 <sect2>
177 <title>Working with multiple branches</title>
179 <para id="x_45d">Projects of any significant size naturally tend to make
180 progress on several fronts simultaneously. In the case of
181 software, it's common for a project to go through periodic
182 official releases. A release might then go into
183 <quote>maintenance mode</quote> for a while after its first
184 publication; maintenance releases tend to contain only bug
185 fixes, not new features. In parallel with these maintenance
186 releases, one or more future releases may be under
187 development. People normally use the word
188 <quote>branch</quote> to refer to one of these many slightly
189 different directions in which development is
190 proceeding.</para>
192 <para id="x_45e">Mercurial is particularly well suited to managing a number
193 of simultaneous, but not identical, branches. Each
194 <quote>development direction</quote> can live in its own
195 central repository, and you can merge changes from one to
196 another as the need arises. Because repositories are
197 independent of each other, unstable changes in a development
198 branch will never affect a stable branch unless someone
199 explicitly merges those changes in.</para>
201 <para id="x_45f">Here's an example of how this can work in practice. Let's
202 say you have one <quote>main branch</quote> on a central
203 server.</para>
205 &interaction.branching.init;
207 <para id="x_460">People clone it, make changes locally, test them, and push
208 them back.</para>
210 <para id="x_461">Once the main branch reaches a release milestone, you can
211 use the <command role="hg-cmd">hg tag</command> command to
212 give a permanent name to the milestone revision.</para>
214 &interaction.branching.tag;
216 <para id="x_462">Let's say some ongoing
217 development occurs on the main branch.</para>
219 &interaction.branching.main;
221 <para id="x_463">Using the tag that was recorded at the milestone, people
222 who clone that repository at any time in the future can use
223 <command role="hg-cmd">hg update</command> to get a copy of
224 the working directory exactly as it was when that tagged
225 revision was committed.</para>
227 &interaction.branching.update;
229 <para id="x_464">In addition, immediately after the main branch is tagged,
230 someone can then clone the main branch on the server to a new
231 <quote>stable</quote> branch, also on the server.</para>
233 &interaction.branching.clone;
235 <para id="x_465">Someone who needs to make a change to the stable branch
236 can then clone <emphasis>that</emphasis> repository, make
237 their changes, commit, and push their changes back there.</para>
239 &interaction.branching.stable;
241 <para id="x_466">Because Mercurial repositories are independent, and
242 Mercurial doesn't move changes around automatically, the
243 stable and main branches are <emphasis>isolated</emphasis>
244 from each other. The changes that you made on the main branch
245 don't <quote>leak</quote> to the stable branch, and vice
246 versa.</para>
248 <para id="x_467">You'll often want all of your bugfixes on the stable
249 branch to show up on the main branch, too. Rather than
250 rewrite a bugfix on the main branch, you can simply pull and
251 merge changes from the stable to the main branch, and
252 Mercurial will bring those bugfixes in for you.</para>
254 &interaction.branching.merge;
256 <para id="x_468">The main branch will still contain changes that are not on
257 the stable branch, but it will also contain all of the
258 bugfixes from the stable branch. The stable branch remains
259 unaffected by these changes.</para>
261 </sect2>
262 <sect2>
263 <title>Feature branches</title>
265 <para id="x_469">For larger projects, an effective way to manage change is
266 to break up a team into smaller groups. Each group has a
267 shared branch of its own, cloned from a single
268 <quote>master</quote> branch used by the entire project.
269 People working on an individual branch are typically quite
270 isolated from developments on other branches.</para>
272 <figure id="fig:collab:feature-branches">
273 <title>Feature branches</title>
274 <mediaobject>
275 <imageobject><imagedata width="100%" fileref="figs/feature-branches.png"/></imageobject>
276 <textobject><phrase>XXX add text</phrase></textobject>
277 </mediaobject>
278 </figure>
280 <para id="x_46b">When a particular feature is deemed to be in suitable
281 shape, someone on that feature team pulls and merges from the
282 master branch into the feature branch, then pushes back up to
283 the master branch.</para>
285 </sect2>
286 <sect2>
287 <title>The release train</title>
289 <para id="x_46c">Some projects are organised on a <quote>train</quote>
290 basis: a release is scheduled to happen every few months, and
291 whatever features are ready when the <quote>train</quote> is
292 ready to leave are allowed in.</para>
294 <para id="x_46d">This model resembles working with feature branches. The
295 difference is that when a feature branch misses a train,
296 someone on the feature team pulls and merges the changes that
297 went out on that train release into the feature branch, and
298 the team continues its work on top of that release so that
299 their feature can make the next release.</para>
301 </sect2>
302 <sect2>
303 <title>The Linux kernel model</title>
305 <para id="x_46e">The development of the Linux kernel has a shallow
306 hierarchical structure, surrounded by a cloud of apparent
307 chaos. Because most Linux developers use
308 <command>git</command>, a distributed revision control tool
309 with capabilities similar to Mercurial, it's useful to
310 describe the way work flows in that environment; if you like
311 the ideas, the approach translates well across tools.</para>
313 <para id="x_46f">At the center of the community sits Linus Torvalds, the
314 creator of Linux. He publishes a single source repository
315 that is considered the <quote>authoritative</quote> current
316 tree by the entire developer community. Anyone can clone
317 Linus's tree, but he is very choosy about whose trees he pulls
318 from.</para>
320 <para id="x_470">Linus has a number of <quote>trusted lieutenants</quote>.
321 As a general rule, he pulls whatever changes they publish, in
322 most cases without even reviewing those changes. Some of
323 those lieutenants are generally agreed to be
324 <quote>maintainers</quote>, responsible for specific
325 subsystems within the kernel. If a random kernel hacker wants
326 to make a change to a subsystem that they want to end up in
327 Linus's tree, they must find out who the subsystem's
328 maintainer is, and ask that maintainer to take their change.
329 If the maintainer reviews their changes and agrees to take
330 them, they'll pass them along to Linus in due course.</para>
332 <para id="x_471">Individual lieutenants have their own approaches to
333 reviewing, accepting, and publishing changes; and for deciding
334 when to feed them to Linus. In addition, there are several
335 well known branches that people use for different purposes.
336 For example, a few people maintain <quote>stable</quote>
337 repositories of older versions of the kernel, to which they
338 apply critical fixes as needed. Some maintainers publish
339 multiple trees: one for experimental changes; one for changes
340 that they are about to feed upstream; and so on. Others just
341 publish a single tree.</para>
343 <para id="x_472">This model has two notable features. The first is that
344 it's <quote>pull only</quote>. You have to ask, convince, or
345 beg another developer to take a change from you, because there
346 are almost no trees to which more than one person can push,
347 and there's no way to push changes into a tree that someone
348 else controls.</para>
350 <para id="x_473">The second is that it's based on reputation and acclaim.
351 If you're an unknown, Linus will probably ignore changes from
352 you without even responding. But a subsystem maintainer will
353 probably review them, and will likely take them if they pass
354 their criteria for suitability. The more <quote>good</quote>
355 changes you contribute to a maintainer, the more likely they
356 are to trust your judgment and accept your changes. If you're
357 well-known and maintain a long-lived branch for something
358 Linus hasn't yet accepted, people with similar interests may
359 pull your changes regularly to keep up with your work.</para>
361 <para id="x_474">Reputation and acclaim don't necessarily cross subsystem
362 or <quote>people</quote> boundaries. If you're a respected
363 but specialised storage hacker, and you try to fix a
364 networking bug, that change will receive a level of scrutiny
365 from a network maintainer comparable to a change from a
366 complete stranger.</para>
368 <para id="x_475">To people who come from more orderly project backgrounds,
369 the comparatively chaotic Linux kernel development process
370 often seems completely insane. It's subject to the whims of
371 individuals; people make sweeping changes whenever they deem
372 it appropriate; and the pace of development is astounding.
373 And yet Linux is a highly successful, well-regarded piece of
374 software.</para>
376 </sect2>
377 <sect2>
378 <title>Pull-only versus shared-push collaboration</title>
380 <para id="x_476">A perpetual source of heat in the open source community is
381 whether a development model in which people only ever pull
382 changes from others is <quote>better than</quote> one in which
383 multiple people can push changes to a shared
384 repository.</para>
386 <para id="x_477">Typically, the backers of the shared-push model use tools
387 that actively enforce this approach. If you're using a
388 centralised revision control tool such as Subversion, there's
389 no way to make a choice over which model you'll use: the tool
390 gives you shared-push, and if you want to do anything else,
391 you'll have to roll your own approach on top (such as applying
392 a patch by hand).</para>
394 <para id="x_478">A good distributed revision control tool, such as
395 Mercurial, will support both models. You and your
396 collaborators can then structure how you work together based
397 on your own needs and preferences, not on what contortions
398 your tools force you into.</para>
400 </sect2>
401 <sect2>
402 <title>Where collaboration meets branch management</title>
404 <para id="x_479">Once you and your team set up some shared
405 repositories and start propagating changes back and forth
406 between local and shared repos, you begin to face a related,
407 but slightly different challenge: that of managing the
408 multiple directions in which your team may be moving at once.
409 Even though this subject is intimately related to how your
410 team collaborates, it's dense enough to merit treatment of its
411 own, in <xref linkend="chap:branch"/>.</para>
413 </sect2>
414 </sect1>
415 <sect1>
416 <title>The technical side of sharing</title>
418 <para id="x_47a">The remainder of this chapter is devoted to the question of
419 serving data to your collaborators.</para>
421 </sect1>
422 <sect1 id="sec:collab:serve">
423 <title>Informal sharing with <command role="hg-cmd">hg
424 serve</command></title>
426 <para id="x_47b">Mercurial's <command role="hg-cmd">hg serve</command>
427 command is wonderfully suited to small, tight-knit, and
428 fast-paced group environments. It also provides a great way to
429 get a feel for using Mercurial commands over a network.</para>
431 <para id="x_47c">Run <command role="hg-cmd">hg serve</command> inside a
432 repository, and in under a second it will bring up a specialised
433 HTTP server; this will accept connections from any client, and
434 serve up data for that repository until you terminate it.
435 Anyone who knows the URL of the server you just started, and can
436 talk to your computer over the network, can then use a web
437 browser or Mercurial to read data from that repository. A URL
438 for a <command role="hg-cmd">hg serve</command> instance running
439 on a laptop is likely to look something like
440 <literal>http://my-laptop.local:8000/</literal>.</para>
442 <para id="x_47d">The <command role="hg-cmd">hg serve</command> command is
443 <emphasis>not</emphasis> a general-purpose web server. It can do
444 only two things:</para>
445 <itemizedlist>
446 <listitem><para id="x_47e">Allow people to browse the history of the
447 repository it's serving, from their normal web
448 browsers.</para>
449 </listitem>
450 <listitem><para id="x_47f">Speak Mercurial's wire protocol, so that people
451 can <command role="hg-cmd">hg clone</command> or <command
452 role="hg-cmd">hg pull</command> changes from that
453 repository.</para>
454 </listitem></itemizedlist>
455 <para id="x_480">In particular, <command role="hg-cmd">hg serve</command>
456 won't allow remote users to <emphasis>modify</emphasis> your
457 repository. It's intended for read-only use.</para>
459 <para id="x_481">If you're getting started with Mercurial, there's nothing to
460 prevent you from using <command role="hg-cmd">hg serve</command>
461 to serve up a repository on your own computer, then use commands
462 like <command role="hg-cmd">hg clone</command>, <command
463 role="hg-cmd">hg incoming</command>, and so on to talk to that
464 server as if the repository was hosted remotely. This can help
465 you to quickly get acquainted with using commands on
466 network-hosted repositories.</para>
468 <sect2>
469 <title>A few things to keep in mind</title>
471 <para id="x_482">Because it provides unauthenticated read access to all
472 clients, you should only use <command role="hg-cmd">hg
473 serve</command> in an environment where you either don't
474 care, or have complete control over, who can access your
475 network and pull data from your repository.</para>
477 <para id="x_483">The <command role="hg-cmd">hg serve</command> command
478 knows nothing about any firewall software you might have
479 installed on your system or network. It cannot detect or
480 control your firewall software. If other people are unable to
481 talk to a running <command role="hg-cmd">hg serve</command>
482 instance, the second thing you should do
483 (<emphasis>after</emphasis> you make sure that they're using
484 the correct URL) is check your firewall configuration.</para>
486 <para id="x_484">By default, <command role="hg-cmd">hg serve</command>
487 listens for incoming connections on port 8000. If another
488 process is already listening on the port you want to use, you
489 can specify a different port to listen on using the <option
490 role="hg-opt-serve">-p</option> option.</para>
492 <para id="x_485">Normally, when <command role="hg-cmd">hg serve</command>
493 starts, it prints no output, which can be a bit unnerving. If
494 you'd like to confirm that it is indeed running correctly, and
495 find out what URL you should send to your collaborators, start
496 it with the <option role="hg-opt-global">-v</option>
497 option.</para>
499 </sect2>
500 </sect1>
501 <sect1 id="sec:collab:ssh">
502 <title>Using the Secure Shell (ssh) protocol</title>
504 <para id="x_486">You can pull and push changes securely over a network
505 connection using the Secure Shell (<literal>ssh</literal>)
506 protocol. To use this successfully, you may have to do a little
507 bit of configuration on the client or server sides.</para>
509 <para id="x_487">If you're not familiar with ssh, it's a network protocol
510 that lets you securely communicate with another computer. To
511 use it with Mercurial, you'll be setting up one or more user
512 accounts on a server so that remote users can log in and execute
513 commands.</para>
515 <para id="x_488">(If you <emphasis>are</emphasis> familiar with ssh, you'll
516 probably find some of the material that follows to be elementary
517 in nature.)</para>
519 <sect2>
520 <title>How to read and write ssh URLs</title>
522 <para id="x_489">An ssh URL tends to look like this:</para>
523 <programlisting>ssh://bos@hg.serpentine.com:22/hg/hgbook</programlisting>
524 <orderedlist>
525 <listitem><para id="x_48a">The <quote><literal>ssh://</literal></quote>
526 part tells Mercurial to use the ssh protocol.</para>
527 </listitem>
528 <listitem><para id="x_48b">The <quote><literal>bos@</literal></quote>
529 component indicates what username to log into the server
530 as. You can leave this out if the remote username is the
531 same as your local username.</para>
532 </listitem>
533 <listitem><para id="x_48c">The
534 <quote><literal>hg.serpentine.com</literal></quote> gives
535 the hostname of the server to log into.</para>
536 </listitem>
537 <listitem><para id="x_48d">The <quote>:22</quote> identifies the port
538 number to connect to the server on. The default port is
539 22, so you only need to specify a colon and port number if
540 you're <emphasis>not</emphasis> using port 22.</para>
541 </listitem>
542 <listitem><para id="x_48e">The remainder of the URL is the local path to
543 the repository on the server.</para>
544 </listitem></orderedlist>
546 <para id="x_48f">There's plenty of scope for confusion with the path
547 component of ssh URLs, as there is no standard way for tools
548 to interpret it. Some programs behave differently than others
549 when dealing with these paths. This isn't an ideal situation,
550 but it's unlikely to change. Please read the following
551 paragraphs carefully.</para>
553 <para id="x_490">Mercurial treats the path to a repository on the server as
554 relative to the remote user's home directory. For example, if
555 user <literal>foo</literal> on the server has a home directory
556 of <filename class="directory">/home/foo</filename>, then an
557 ssh URL that contains a path component of <filename
558 class="directory">bar</filename> <emphasis>really</emphasis>
559 refers to the directory <filename
560 class="directory">/home/foo/bar</filename>.</para>
562 <para id="x_491">If you want to specify a path relative to another user's
563 home directory, you can use a path that starts with a tilde
564 character followed by the user's name (let's call them
565 <literal>otheruser</literal>), like this.</para>
566 <programlisting>ssh://server/~otheruser/hg/repo</programlisting>
568 <para id="x_492">And if you really want to specify an
569 <emphasis>absolute</emphasis> path on the server, begin the
570 path component with two slashes, as in this example.</para>
571 <programlisting>ssh://server//absolute/path</programlisting>
573 </sect2>
574 <sect2>
575 <title>Finding an ssh client for your system</title>
577 <para id="x_493">Almost every Unix-like system comes with OpenSSH
578 preinstalled. If you're using such a system, run
579 <literal>which ssh</literal> to find out if the
580 <command>ssh</command> command is installed (it's usually in
581 <filename class="directory">/usr/bin</filename>). In the
582 unlikely event that it isn't present, take a look at your
583 system documentation to figure out how to install it.</para>
585 <para id="x_494">On Windows, you'll first need to download a suitable ssh
586 client. There are two alternatives.</para>
587 <itemizedlist>
588 <listitem><para id="x_495">Simon Tatham's excellent PuTTY package
589 <citation>web:putty</citation> provides a complete suite
590 of ssh client commands.</para>
591 </listitem>
592 <listitem><para id="x_496">If you have a high tolerance for pain, you can
593 use the Cygwin port of OpenSSH.</para>
594 </listitem></itemizedlist>
595 <para id="x_497">In either case, you'll need to edit your <filename
596 role="special">hg.ini</filename> file to
597 tell Mercurial where to find the actual client command. For
598 example, if you're using PuTTY, you'll need to use the
599 <command>plink</command> command as a command-line ssh
600 client.</para>
601 <programlisting>[ui]
602 ssh = C:/path/to/plink.exe -ssh -i "C:/path/to/my/private/key"</programlisting>
604 <note>
605 <para id="x_498"> The path to <command>plink</command> shouldn't contain
606 any whitespace characters, or Mercurial may not be able to
607 run it correctly (so putting it in <filename
608 class="directory">C:\Program Files</filename> is probably
609 not a good idea).</para>
610 </note>
612 </sect2>
613 <sect2>
614 <title>Generating a key pair</title>
616 <para id="x_499">To avoid the need to repetitively type a password every
617 time you need to use your ssh client, I recommend generating a
618 key pair. On a Unix-like system, the
619 <command>ssh-keygen</command> command will do the trick. On
620 Windows, if you're using PuTTY, the
621 <command>puttygen</command> command is what you'll
622 need.</para>
624 <para id="x_49a">When you generate a key pair, it's usually
625 <emphasis>highly</emphasis> advisable to protect it with a
626 passphrase. (The only time that you might not want to do this
627 is when you're using the ssh protocol for automated tasks on a
628 secure network.)</para>
630 <para id="x_49b">Simply generating a key pair isn't enough, however.
631 You'll need to add the public key to the set of authorised
632 keys for whatever user you're logging in remotely as. For
633 servers using OpenSSH (the vast majority), this will mean
634 adding the public key to a list in a file called <filename
635 role="special">authorized_keys</filename> in their <filename
636 role="special" class="directory">.ssh</filename>
637 directory.</para>
639 <para id="x_49c">On a Unix-like system, your public key will have a
640 <filename>.pub</filename> extension. If you're using
641 <command>puttygen</command> on Windows, you can save the
642 public key to a file of your choosing, or paste it from the
643 window it's displayed in straight into the <filename
644 role="special">authorized_keys</filename> file.</para>
646 </sect2>
647 <sect2>
648 <title>Using an authentication agent</title>
650 <para id="x_49d">An authentication agent is a daemon that stores
651 passphrases in memory (so it will forget passphrases if you
652 log out and log back in again). An ssh client will notice if
653 it's running, and query it for a passphrase. If there's no
654 authentication agent running, or the agent doesn't store the
655 necessary passphrase, you'll have to type your passphrase
656 every time Mercurial tries to communicate with a server on
657 your behalf (e.g. whenever you pull or push changes).</para>
659 <para id="x_49e">The downside of storing passphrases in an agent is that
660 it's possible for a well-prepared attacker to recover the
661 plain text of your passphrases, in some cases even if your
662 system has been power-cycled. You should make your own
663 judgment as to whether this is an acceptable risk. It
664 certainly saves a lot of repeated typing.</para>
666 <para id="x_49f">On Unix-like systems, the agent is called
667 <command>ssh-agent</command>, and it's often run automatically
668 for you when you log in. You'll need to use the
669 <command>ssh-add</command> command to add passphrases to the
670 agent's store. On Windows, if you're using PuTTY, the
671 <command>pageant</command> command acts as the agent. It adds
672 an icon to your system tray that will let you manage stored
673 passphrases.</para>
675 </sect2>
676 <sect2>
677 <title>Configuring the server side properly</title>
679 <para id="x_4a0">Because ssh can be fiddly to set up if you're new to it,
680 there's a variety of things that can go wrong. Add Mercurial
681 on top, and there's plenty more scope for head-scratching.
682 Most of these potential problems occur on the server side, not
683 the client side. The good news is that once you've gotten a
684 configuration working, it will usually continue to work
685 indefinitely.</para>
687 <para id="x_4a1">Before you try using Mercurial to talk to an ssh server,
688 it's best to make sure that you can use the normal
689 <command>ssh</command> or <command>putty</command> command to
690 talk to the server first. If you run into problems with using
691 these commands directly, Mercurial surely won't work. Worse,
692 it will obscure the underlying problem. Any time you want to
693 debug ssh-related Mercurial problems, you should drop back to
694 making sure that plain ssh client commands work first,
695 <emphasis>before</emphasis> you worry about whether there's a
696 problem with Mercurial.</para>
698 <para id="x_4a2">The first thing to be sure of on the server side is that
699 you can actually log in from another machine at all. If you
700 can't use <command>ssh</command> or <command>putty</command>
701 to log in, the error message you get may give you a few hints
702 as to what's wrong. The most common problems are as
703 follows.</para>
704 <itemizedlist>
705 <listitem><para id="x_4a3">If you get a <quote>connection refused</quote>
706 error, either there isn't an SSH daemon running on the
707 server at all, or it's inaccessible due to firewall
708 configuration.</para>
709 </listitem>
710 <listitem><para id="x_4a4">If you get a <quote>no route to host</quote>
711 error, you either have an incorrect address for the server
712 or a seriously locked down firewall that won't admit its
713 existence at all.</para>
714 </listitem>
715 <listitem><para id="x_4a5">If you get a <quote>permission denied</quote>
716 error, you may have mistyped the username on the server,
717 or you could have mistyped your key's passphrase or the
718 remote user's password.</para>
719 </listitem></itemizedlist>
720 <para id="x_4a6">In summary, if you're having trouble talking to the
721 server's ssh daemon, first make sure that one is running at
722 all. On many systems it will be installed, but disabled, by
723 default. Once you're done with this step, you should then
724 check that the server's firewall is configured to allow
725 incoming connections on the port the ssh daemon is listening
726 on (usually 22). Don't worry about more exotic possibilities
727 for misconfiguration until you've checked these two
728 first.</para>
730 <para id="x_4a7">If you're using an authentication agent on the client side
731 to store passphrases for your keys, you ought to be able to
732 log into the server without being prompted for a passphrase or
733 a password. If you're prompted for a passphrase, there are a
734 few possible culprits.</para>
735 <itemizedlist>
736 <listitem><para id="x_4a8">You might have forgotten to use
737 <command>ssh-add</command> or <command>pageant</command>
738 to store the passphrase.</para>
739 </listitem>
740 <listitem><para id="x_4a9">You might have stored the passphrase for the
741 wrong key.</para>
742 </listitem></itemizedlist>
743 <para id="x_4aa">If you're being prompted for the remote user's password,
744 there are another few possible problems to check.</para>
745 <itemizedlist>
746 <listitem><para id="x_4ab">Either the user's home directory or their
747 <filename role="special" class="directory">.ssh</filename>
748 directory might have excessively liberal permissions. As
749 a result, the ssh daemon will not trust or read their
750 <filename role="special">authorized_keys</filename> file.
751 For example, a group-writable home or <filename
752 role="special" class="directory">.ssh</filename>
753 directory will often cause this symptom.</para>
754 </listitem>
755 <listitem><para id="x_4ac">The user's <filename
756 role="special">authorized_keys</filename> file may have
757 a problem. If anyone other than the user owns or can write
758 to that file, the ssh daemon will not trust or read
759 it.</para>
760 </listitem></itemizedlist>
762 <para id="x_4ad">In the ideal world, you should be able to run the
763 following command successfully, and it should print exactly
764 one line of output, the current date and time.</para>
765 <programlisting>ssh myserver date</programlisting>
767 <para id="x_4ae">If, on your server, you have login scripts that print
768 banners or other junk even when running non-interactive
769 commands like this, you should fix them before you continue,
770 so that they only print output if they're run interactively.
771 Otherwise these banners will at least clutter up Mercurial's
772 output. Worse, they could potentially cause problems with
773 running Mercurial commands remotely. Mercurial makes tries to
774 detect and ignore banners in non-interactive
775 <command>ssh</command> sessions, but it is not foolproof. (If
776 you're editing your login scripts on your server, the usual
777 way to see if a login script is running in an interactive
778 shell is to check the return code from the command
779 <literal>tty -s</literal>.)</para>
781 <para id="x_4af">Once you've verified that plain old ssh is working with
782 your server, the next step is to ensure that Mercurial runs on
783 the server. The following command should run
784 successfully:</para>
786 <programlisting>ssh myserver hg version</programlisting>
788 <para id="x_4b0">If you see an error message instead of normal <command
789 role="hg-cmd">hg version</command> output, this is usually
790 because you haven't installed Mercurial to <filename
791 class="directory">/usr/bin</filename>. Don't worry if this
792 is the case; you don't need to do that. But you should check
793 for a few possible problems.</para>
794 <itemizedlist>
795 <listitem><para id="x_4b1">Is Mercurial really installed on the server at
796 all? I know this sounds trivial, but it's worth
797 checking!</para>
798 </listitem>
799 <listitem><para id="x_4b2">Maybe your shell's search path (usually set
800 via the <envar>PATH</envar> environment variable) is
801 simply misconfigured.</para>
802 </listitem>
803 <listitem><para id="x_4b3">Perhaps your <envar>PATH</envar> environment
804 variable is only being set to point to the location of the
805 <command>hg</command> executable if the login session is
806 interactive. This can happen if you're setting the path
807 in the wrong shell login script. See your shell's
808 documentation for details.</para>
809 </listitem>
810 <listitem><para id="x_4b4">The <envar>PYTHONPATH</envar> environment
811 variable may need to contain the path to the Mercurial
812 Python modules. It might not be set at all; it could be
813 incorrect; or it may be set only if the login is
814 interactive.</para>
815 </listitem></itemizedlist>
817 <para id="x_4b5">If you can run <command role="hg-cmd">hg version</command>
818 over an ssh connection, well done! You've got the server and
819 client sorted out. You should now be able to use Mercurial to
820 access repositories hosted by that username on that server.
821 If you run into problems with Mercurial and ssh at this point,
822 try using the <option role="hg-opt-global">--debug</option>
823 option to get a clearer picture of what's going on.</para>
825 </sect2>
826 <sect2>
827 <title>Using compression with ssh</title>
829 <para id="x_4b6">Mercurial does not compress data when it uses the ssh
830 protocol, because the ssh protocol can transparently compress
831 data. However, the default behaviour of ssh clients is
832 <emphasis>not</emphasis> to request compression.</para>
834 <para id="x_4b7">Over any network other than a fast LAN (even a wireless
835 network), using compression is likely to significantly speed
836 up Mercurial's network operations. For example, over a WAN,
837 someone measured compression as reducing the amount of time
838 required to clone a particularly large repository from 51
839 minutes to 17 minutes.</para>
841 <para id="x_4b8">Both <command>ssh</command> and <command>plink</command>
842 accept a <option role="cmd-opt-ssh">-C</option> option which
843 turns on compression. You can easily edit your <filename
844 role="special">~/.hgrc</filename> to enable compression for
845 all of Mercurial's uses of the ssh protocol.</para>
846 <programlisting>[ui]
847 ssh = ssh -C</programlisting>
849 <para id="x_4b9">If you use <command>ssh</command>, you can configure it to
850 always use compression when talking to your server. To do
851 this, edit your <filename
852 role="special">.ssh/config</filename> file (which may not
853 yet exist), as follows.</para>
854 <programlisting>Host hg
855 Compression yes
856 HostName hg.example.com</programlisting>
857 <para id="x_4ba">This defines an alias, <literal>hg</literal>. When you
858 use it on the <command>ssh</command> command line or in a
859 Mercurial <literal>ssh</literal>-protocol URL, it will cause
860 <command>ssh</command> to connect to
861 <literal>hg.example.com</literal> and use compression. This
862 gives you both a shorter name to type and compression, each of
863 which is a good thing in its own right.</para>
865 </sect2>
866 </sect1>
867 <sect1 id="sec:collab:cgi">
868 <title>Serving over HTTP using CGI</title>
870 <para id="x_4bb">Depending on how ambitious you are, configuring Mercurial's
871 CGI interface can take anything from a few moments to several
872 hours.</para>
874 <para id="x_4bc">We'll begin with the simplest of examples, and work our way
875 towards a more complex configuration. Even for the most basic
876 case, you're almost certainly going to need to read and modify
877 your web server's configuration.</para>
879 <note>
880 <para id="x_4bd"> Configuring a web server is a complex, fiddly, and
881 highly system-dependent activity. I can't possibly give you
882 instructions that will cover anything like all of the cases
883 you will encounter. Please use your discretion and judgment in
884 following the sections below. Be prepared to make plenty of
885 mistakes, and to spend a lot of time reading your server's
886 error logs.</para>
887 </note>
889 <sect2>
890 <title>Web server configuration checklist</title>
892 <para id="x_4be">Before you continue, do take a few moments to check a few
893 aspects of your system's setup.</para>
895 <orderedlist>
896 <listitem><para id="x_4bf">Do you have a web server installed at all?
897 Mac OS X ships with Apache, but many other systems may not
898 have a web server installed.</para>
899 </listitem>
900 <listitem><para id="x_4c0">If you have a web server installed, is it
901 actually running? On most systems, even if one is
902 present, it will be disabled by default.</para>
903 </listitem>
904 <listitem><para id="x_4c1">Is your server configured to allow you to run
905 CGI programs in the directory where you plan to do so?
906 Most servers default to explicitly disabling the ability
907 to run CGI programs.</para>
908 </listitem></orderedlist>
910 <para id="x_4c2">If you don't have a web server installed, and don't have
911 substantial experience configuring Apache, you should consider
912 using the <literal>lighttpd</literal> web server instead of
913 Apache. Apache has a well-deserved reputation for baroque and
914 confusing configuration. While <literal>lighttpd</literal> is
915 less capable in some ways than Apache, most of these
916 capabilities are not relevant to serving Mercurial
917 repositories. And <literal>lighttpd</literal> is undeniably
918 <emphasis>much</emphasis> easier to get started with than
919 Apache.</para>
921 </sect2>
922 <sect2>
923 <title>Basic CGI configuration</title>
925 <para id="x_4c3">On Unix-like systems, it's common for users to have a
926 subdirectory named something like <filename
927 class="directory">public_html</filename> in their home
928 directory, from which they can serve up web pages. A file
929 named <filename>foo</filename> in this directory will be
930 accessible at a URL of the form
931 <literal>http://www.example.com/username/foo</literal>.</para>
933 <para id="x_4c4">To get started, find the <filename
934 role="special">hgweb.cgi</filename> script that should be
935 present in your Mercurial installation. If you can't quickly
936 find a local copy on your system, simply download one from the
937 master Mercurial repository at <ulink
938 url="http://www.selenic.com/repo/hg/raw-file/tip/hgweb.cgi">http://www.selenic.com/repo/hg/raw-file/tip/hgweb.cgi</ulink>.</para>
940 <para id="x_4c5">You'll need to copy this script into your <filename
941 class="directory">public_html</filename> directory, and
942 ensure that it's executable.</para>
943 <programlisting>cp .../hgweb.cgi ~/public_html
944 chmod 755 ~/public_html/hgweb.cgi</programlisting>
945 <para id="x_4c6">The <literal>755</literal> argument to
946 <command>chmod</command> is a little more general than just
947 making the script executable: it ensures that the script is
948 executable by anyone, and that <quote>group</quote> and
949 <quote>other</quote> write permissions are
950 <emphasis>not</emphasis> set. If you were to leave those
951 write permissions enabled, Apache's <literal>suexec</literal>
952 subsystem would likely refuse to execute the script. In fact,
953 <literal>suexec</literal> also insists that the
954 <emphasis>directory</emphasis> in which the script resides
955 must not be writable by others.</para>
956 <programlisting>chmod 755 ~/public_html</programlisting>
958 <sect3 id="sec:collab:wtf">
959 <title>What could <emphasis>possibly</emphasis> go
960 wrong?</title>
962 <para id="x_4c7">Once you've copied the CGI script into place, go into a
963 web browser, and try to open the URL <ulink
964 url="http://myhostname/
965 myuser/hgweb.cgi">http://myhostname/
966 myuser/hgweb.cgi</ulink>, <emphasis>but</emphasis> brace
967 yourself for instant failure. There's a high probability
968 that trying to visit this URL will fail, and there are many
969 possible reasons for this. In fact, you're likely to
970 stumble over almost every one of the possible errors below,
971 so please read carefully. The following are all of the
972 problems I ran into on a system running Fedora 7, with a
973 fresh installation of Apache, and a user account that I
974 created specially to perform this exercise.</para>
976 <para id="x_4c8">Your web server may have per-user directories disabled.
977 If you're using Apache, search your config file for a
978 <literal>UserDir</literal> directive. If there's none
979 present, per-user directories will be disabled. If one
980 exists, but its value is <literal>disabled</literal>, then
981 per-user directories will be disabled. Otherwise, the
982 string after <literal>UserDir</literal> gives the name of
983 the subdirectory that Apache will look in under your home
984 directory, for example <filename
985 class="directory">public_html</filename>.</para>
987 <para id="x_4c9">Your file access permissions may be too restrictive.
988 The web server must be able to traverse your home directory
989 and directories under your <filename
990 class="directory">public_html</filename> directory, and
991 read files under the latter too. Here's a quick recipe to
992 help you to make your permissions more appropriate.</para>
993 <programlisting>chmod 755 ~
994 find ~/public_html -type d -print0 | xargs -0r chmod 755
995 find ~/public_html -type f -print0 | xargs -0r chmod 644</programlisting>
997 <para id="x_4ca">The other possibility with permissions is that you might
998 get a completely empty window when you try to load the
999 script. In this case, it's likely that your access
1000 permissions are <emphasis>too permissive</emphasis>. Apache's
1001 <literal>suexec</literal> subsystem won't execute a script
1002 that's group- or world-writable, for example.</para>
1004 <para id="x_4cb">Your web server may be configured to disallow execution
1005 of CGI programs in your per-user web directory. Here's
1006 Apache's default per-user configuration from my Fedora
1007 system.</para>
1009 &ch06-apache-config.lst;
1011 <para id="x_4cc">If you find a similar-looking
1012 <literal>Directory</literal> group in your Apache
1013 configuration, the directive to look at inside it is
1014 <literal>Options</literal>. Add <literal>ExecCGI</literal>
1015 to the end of this list if it's missing, and restart the web
1016 server.</para>
1018 <para id="x_4cd">If you find that Apache serves you the text of the CGI
1019 script instead of executing it, you may need to either
1020 uncomment (if already present) or add a directive like
1021 this.</para>
1022 <programlisting>AddHandler cgi-script .cgi</programlisting>
1024 <para id="x_4ce">The next possibility is that you might be served with a
1025 colourful Python backtrace claiming that it can't import a
1026 <literal>mercurial</literal>-related module. This is
1027 actually progress! The server is now capable of executing
1028 your CGI script. This error is only likely to occur if
1029 you're running a private installation of Mercurial, instead
1030 of a system-wide version. Remember that the web server runs
1031 the CGI program without any of the environment variables
1032 that you take for granted in an interactive session. If
1033 this error happens to you, edit your copy of <filename
1034 role="special">hgweb.cgi</filename> and follow the
1035 directions inside it to correctly set your
1036 <envar>PYTHONPATH</envar> environment variable.</para>
1038 <para id="x_4cf">Finally, you are <emphasis>certain</emphasis> to by
1039 served with another colourful Python backtrace: this one
1040 will complain that it can't find <filename
1041 class="directory">/path/to/repository</filename>. Edit
1042 your <filename role="special">hgweb.cgi</filename> script
1043 and replace the <filename
1044 class="directory">/path/to/repository</filename> string
1045 with the complete path to the repository you want to serve
1046 up.</para>
1048 <para id="x_4d0">At this point, when you try to reload the page, you
1049 should be presented with a nice HTML view of your
1050 repository's history. Whew!</para>
1052 </sect3>
1053 <sect3>
1054 <title>Configuring lighttpd</title>
1056 <para id="x_4d1">To be exhaustive in my experiments, I tried configuring
1057 the increasingly popular <literal>lighttpd</literal> web
1058 server to serve the same repository as I described with
1059 Apache above. I had already overcome all of the problems I
1060 outlined with Apache, many of which are not server-specific.
1061 As a result, I was fairly sure that my file and directory
1062 permissions were good, and that my <filename
1063 role="special">hgweb.cgi</filename> script was properly
1064 edited.</para>
1066 <para id="x_4d2">Once I had Apache running, getting
1067 <literal>lighttpd</literal> to serve the repository was a
1068 snap (in other words, even if you're trying to use
1069 <literal>lighttpd</literal>, you should read the Apache
1070 section). I first had to edit the
1071 <literal>mod_access</literal> section of its config file to
1072 enable <literal>mod_cgi</literal> and
1073 <literal>mod_userdir</literal>, both of which were disabled
1074 by default on my system. I then added a few lines to the
1075 end of the config file, to configure these modules.</para>
1076 <programlisting>userdir.path = "public_html"
1077 cgi.assign = (".cgi" => "" )</programlisting>
1078 <para id="x_4d3">With this done, <literal>lighttpd</literal> ran
1079 immediately for me. If I had configured
1080 <literal>lighttpd</literal> before Apache, I'd almost
1081 certainly have run into many of the same system-level
1082 configuration problems as I did with Apache. However, I
1083 found <literal>lighttpd</literal> to be noticeably easier to
1084 configure than Apache, even though I've used Apache for over
1085 a decade, and this was my first exposure to
1086 <literal>lighttpd</literal>.</para>
1088 </sect3>
1089 </sect2>
1090 <sect2>
1091 <title>Sharing multiple repositories with one CGI script</title>
1093 <para id="x_4d4">The <filename role="special">hgweb.cgi</filename> script
1094 only lets you publish a single repository, which is an
1095 annoying restriction. If you want to publish more than one
1096 without wracking yourself with multiple copies of the same
1097 script, each with different names, a better choice is to use
1098 the <filename role="special">hgwebdir.cgi</filename>
1099 script.</para>
1101 <para id="x_4d5">The procedure to configure <filename
1102 role="special">hgwebdir.cgi</filename> is only a little more
1103 involved than for <filename
1104 role="special">hgweb.cgi</filename>. First, you must obtain
1105 a copy of the script. If you don't have one handy, you can
1106 download a copy from the master Mercurial repository at <ulink
1107 url="http://www.selenic.com/repo/hg/raw-file/tip/hgwebdir.cgi">http://www.selenic.com/repo/hg/raw-file/tip/hgwebdir.cgi</ulink>.</para>
1109 <para id="x_4d6">You'll need to copy this script into your <filename
1110 class="directory">public_html</filename> directory, and
1111 ensure that it's executable.</para>
1113 <programlisting>cp .../hgwebdir.cgi ~/public_html
1114 chmod 755 ~/public_html ~/public_html/hgwebdir.cgi</programlisting>
1116 <para id="x_4d7">With basic configuration out of the way, try to
1117 visit <ulink url="http://myhostname/
1118 myuser/hgwebdir.cgi">http://myhostname/
1119 myuser/hgwebdir.cgi</ulink> in your browser. It should
1120 display an empty list of repositories. If you get a blank
1121 window or error message, try walking through the list of
1122 potential problems in <xref
1123 linkend="sec:collab:wtf"/>.</para>
1125 <para id="x_4d8">The <filename role="special">hgwebdir.cgi</filename>
1126 script relies on an external configuration file. By default,
1127 it searches for a file named <filename
1128 role="special">hgweb.config</filename> in the same directory
1129 as itself. You'll need to create this file, and make it
1130 world-readable. The format of the file is similar to a
1131 Windows <quote>ini</quote> file, as understood by Python's
1132 <literal>ConfigParser</literal>
1133 <citation>web:configparser</citation> module.</para>
1135 <para id="x_4d9">The easiest way to configure <filename
1136 role="special">hgwebdir.cgi</filename> is with a section
1137 named <literal>collections</literal>. This will automatically
1138 publish <emphasis>every</emphasis> repository under the
1139 directories you name. The section should look like
1140 this:</para>
1141 <programlisting>[collections]
1142 /my/root = /my/root</programlisting>
1143 <para id="x_4da">Mercurial interprets this by looking at the directory name
1144 on the <emphasis>right</emphasis> hand side of the
1145 <quote><literal>=</literal></quote> sign; finding repositories
1146 in that directory hierarchy; and using the text on the
1147 <emphasis>left</emphasis> to strip off matching text from the
1148 names it will actually list in the web interface. The
1149 remaining component of a path after this stripping has
1150 occurred is called a <quote>virtual path</quote>.</para>
1152 <para id="x_4db">Given the example above, if we have a repository whose
1153 local path is <filename
1154 class="directory">/my/root/this/repo</filename>, the CGI
1155 script will strip the leading <filename
1156 class="directory">/my/root</filename> from the name, and
1157 publish the repository with a virtual path of <filename
1158 class="directory">this/repo</filename>. If the base URL for
1159 our CGI script is <ulink url="http://myhostname/
1160 myuser/hgwebdir.cgi">http://myhostname/
1161 myuser/hgwebdir.cgi</ulink>, the complete URL for that
1162 repository will be <ulink url="http://myhostname/
1163 myuser/hgwebdir.cgi/this/repo">http://myhostname/
1164 myuser/hgwebdir.cgi/this/repo</ulink>.</para>
1166 <para id="x_4dc">If we replace <filename
1167 class="directory">/my/root</filename> on the left hand side
1168 of this example with <filename
1169 class="directory">/my</filename>, then <filename
1170 role="special">hgwebdir.cgi</filename> will only strip off
1171 <filename class="directory">/my</filename> from the repository
1172 name, and will give us a virtual path of <filename
1173 class="directory">root/this/repo</filename> instead of
1174 <filename class="directory">this/repo</filename>.</para>
1176 <para id="x_4dd">The <filename role="special">hgwebdir.cgi</filename>
1177 script will recursively search each directory listed in the
1178 <literal>collections</literal> section of its configuration
1179 file, but it will <literal>not</literal> recurse into the
1180 repositories it finds.</para>
1182 <para id="x_4de">The <literal>collections</literal> mechanism makes it easy
1183 to publish many repositories in a <quote>fire and
1184 forget</quote> manner. You only need to set up the CGI
1185 script and configuration file one time. Afterwards, you can
1186 publish or unpublish a repository at any time by simply moving
1187 it into, or out of, the directory hierarchy in which you've
1188 configured <filename role="special">hgwebdir.cgi</filename> to
1189 look.</para>
1191 <sect3>
1192 <title>Explicitly specifying which repositories to
1193 publish</title>
1195 <para id="x_4df">In addition to the <literal>collections</literal>
1196 mechanism, the <filename
1197 role="special">hgwebdir.cgi</filename> script allows you
1198 to publish a specific list of repositories. To do so,
1199 create a <literal>paths</literal> section, with contents of
1200 the following form.</para>
1201 <programlisting>[paths]
1202 repo1 = /my/path/to/some/repo
1203 repo2 = /some/path/to/another</programlisting>
1204 <para id="x_4e0">In this case, the virtual path (the component that will
1205 appear in a URL) is on the left hand side of each
1206 definition, while the path to the repository is on the
1207 right. Notice that there does not need to be any
1208 relationship between the virtual path you choose and the
1209 location of a repository in your filesystem.</para>
1211 <para id="x_4e1">If you wish, you can use both the
1212 <literal>collections</literal> and <literal>paths</literal>
1213 mechanisms simultaneously in a single configuration
1214 file.</para>
1216 <note>
1217 <para id="x_4e2"> If multiple repositories have the same virtual path,
1218 <filename role="special">hgwebdir.cgi</filename> will not
1219 report an error. Instead, it will behave
1220 unpredictably.</para>
1221 </note>
1223 </sect3>
1224 </sect2>
1225 <sect2>
1226 <title>Downloading source archives</title>
1228 <para id="x_4e3">Mercurial's web interface lets users download an archive
1229 of any revision. This archive will contain a snapshot of the
1230 working directory as of that revision, but it will not contain
1231 a copy of the repository data.</para>
1233 <para id="x_4e4">By default, this feature is not enabled. To enable it,
1234 you'll need to add an <envar
1235 role="rc-item-web">allow_archive</envar> item to the
1236 <literal role="rc-web">web</literal> section of your <filename
1237 role="special">~/.hgrc</filename>.</para>
1239 </sect2>
1240 <sect2>
1241 <title>Web configuration options</title>
1243 <para id="x_4e5">Mercurial's web interfaces (the <command role="hg-cmd">hg
1244 serve</command> command, and the <filename
1245 role="special">hgweb.cgi</filename> and <filename
1246 role="special">hgwebdir.cgi</filename> scripts) have a
1247 number of configuration options that you can set. These
1248 belong in a section named <literal
1249 role="rc-web">web</literal>.</para>
1250 <itemizedlist>
1251 <listitem><para id="x_4e6"><envar
1252 role="rc-item-web">allow_archive</envar>: Determines
1253 which (if any) archive download mechanisms Mercurial
1254 supports. If you enable this feature, users of the web
1255 interface will be able to download an archive of whatever
1256 revision of a repository they are viewing. To enable the
1257 archive feature, this item must take the form of a
1258 sequence of words drawn from the list below.</para>
1259 <itemizedlist>
1260 <listitem><para id="x_4e7"><literal>bz2</literal>: A
1261 <command>tar</command> archive, compressed using
1262 <literal>bzip2</literal> compression. This has the
1263 best compression ratio, but uses the most CPU time on
1264 the server.</para>
1265 </listitem>
1266 <listitem><para id="x_4e8"><literal>gz</literal>: A
1267 <command>tar</command> archive, compressed using
1268 <literal>gzip</literal> compression.</para>
1269 </listitem>
1270 <listitem><para id="x_4e9"><literal>zip</literal>: A
1271 <command>zip</command> archive, compressed using LZW
1272 compression. This format has the worst compression
1273 ratio, but is widely used in the Windows world.</para>
1274 </listitem>
1275 </itemizedlist>
1276 <para id="x_4ea"> If you provide an empty list, or don't have an
1277 <envar role="rc-item-web">allow_archive</envar> entry at
1278 all, this feature will be disabled. Here is an example of
1279 how to enable all three supported formats.</para>
1280 <programlisting>[web]
1281 allow_archive = bz2 gz zip</programlisting>
1282 </listitem>
1283 <listitem><para id="x_4eb"><envar role="rc-item-web">allowpull</envar>:
1284 Boolean. Determines whether the web interface allows
1285 remote users to <command role="hg-cmd">hg pull</command>
1286 and <command role="hg-cmd">hg clone</command> this
1287 repository over HTTP. If set to <literal>no</literal> or
1288 <literal>false</literal>, only the
1289 <quote>human-oriented</quote> portion of the web interface
1290 is available.</para>
1291 </listitem>
1292 <listitem><para id="x_4ec"><envar role="rc-item-web">contact</envar>:
1293 String. A free-form (but preferably brief) string
1294 identifying the person or group in charge of the
1295 repository. This often contains the name and email
1296 address of a person or mailing list. It often makes sense
1297 to place this entry in a repository's own <filename
1298 role="special">.hg/hgrc</filename> file, but it can make
1299 sense to use in a global <filename
1300 role="special">~/.hgrc</filename> if every repository
1301 has a single maintainer.</para>
1302 </listitem>
1303 <listitem><para id="x_4ed"><envar role="rc-item-web">maxchanges</envar>:
1304 Integer. The default maximum number of changesets to
1305 display in a single page of output.</para>
1306 </listitem>
1307 <listitem><para id="x_4ee"><envar role="rc-item-web">maxfiles</envar>:
1308 Integer. The default maximum number of modified files to
1309 display in a single page of output.</para>
1310 </listitem>
1311 <listitem><para id="x_4ef"><envar role="rc-item-web">stripes</envar>:
1312 Integer. If the web interface displays alternating
1313 <quote>stripes</quote> to make it easier to visually align
1314 rows when you are looking at a table, this number controls
1315 the number of rows in each stripe.</para>
1316 </listitem>
1317 <listitem><para id="x_4f0"><envar
1318 role="rc-item-web">style</envar>: Controls the template
1319 Mercurial uses to display the web interface. Mercurial
1320 ships with two web templates, named
1321 <literal>default</literal> and <literal>gitweb</literal>
1322 (the latter is much more visually attractive). You can
1323 also specify a custom template of your own; see
1324 <xref linkend="chap:template"/> for details. Here, you can
1325 see how to enable the <literal>gitweb</literal>
1326 style.</para>
1327 <programlisting>[web]
1328 style = gitweb</programlisting>
1329 </listitem>
1330 <listitem><para id="x_4f1"><envar role="rc-item-web">templates</envar>:
1331 Path. The directory in which to search for template
1332 files. By default, Mercurial searches in the directory in
1333 which it was installed.</para>
1334 </listitem></itemizedlist>
1335 <para id="x_4f2">If you are using <filename
1336 role="special">hgwebdir.cgi</filename>, you can place a few
1337 configuration items in a <literal role="rc-web">web</literal>
1338 section of the <filename
1339 role="special">hgweb.config</filename> file instead of a
1340 <filename role="special">~/.hgrc</filename> file, for
1341 convenience. These items are <envar
1342 role="rc-item-web">motd</envar> and <envar
1343 role="rc-item-web">style</envar>.</para>
1345 <sect3>
1346 <title>Options specific to an individual repository</title>
1348 <para id="x_4f3">A few <literal role="rc-web">web</literal> configuration
1349 items ought to be placed in a repository's local <filename
1350 role="special">.hg/hgrc</filename>, rather than a user's
1351 or global <filename role="special">~/.hgrc</filename>.</para>
1352 <itemizedlist>
1353 <listitem><para id="x_4f4"><envar
1354 role="rc-item-web">description</envar>: String. A
1355 free-form (but preferably brief) string that describes
1356 the contents or purpose of the repository.</para>
1357 </listitem>
1358 <listitem><para id="x_4f5"><envar role="rc-item-web">name</envar>:
1359 String. The name to use for the repository in the web
1360 interface. This overrides the default name, which is
1361 the last component of the repository's path.</para>
1362 </listitem></itemizedlist>
1364 </sect3>
1365 <sect3>
1366 <title>Options specific to the <command role="hg-cmd">hg
1367 serve</command> command</title>
1369 <para id="x_4f6">Some of the items in the <literal
1370 role="rc-web">web</literal> section of a <filename
1371 role="special">~/.hgrc</filename> file are only for use
1372 with the <command role="hg-cmd">hg serve</command>
1373 command.</para>
1374 <itemizedlist>
1375 <listitem><para id="x_4f7"><envar role="rc-item-web">accesslog</envar>:
1376 Path. The name of a file into which to write an access
1377 log. By default, the <command role="hg-cmd">hg
1378 serve</command> command writes this information to
1379 standard output, not to a file. Log entries are written
1380 in the standard <quote>combined</quote> file format used
1381 by almost all web servers.</para>
1382 </listitem>
1383 <listitem><para id="x_4f8"><envar role="rc-item-web">address</envar>:
1384 String. The local address on which the server should
1385 listen for incoming connections. By default, the server
1386 listens on all addresses.</para>
1387 </listitem>
1388 <listitem><para id="x_4f9"><envar role="rc-item-web">errorlog</envar>:
1389 Path. The name of a file into which to write an error
1390 log. By default, the <command role="hg-cmd">hg
1391 serve</command> command writes this information to
1392 standard error, not to a file.</para>
1393 </listitem>
1394 <listitem><para id="x_4fa"><envar role="rc-item-web">ipv6</envar>:
1395 Boolean. Whether to use the IPv6 protocol. By default,
1396 IPv6 is not used.</para>
1397 </listitem>
1398 <listitem><para id="x_4fb"><envar role="rc-item-web">port</envar>:
1399 Integer. The TCP port number on which the server should
1400 listen. The default port number used is 8000.</para>
1401 </listitem></itemizedlist>
1403 </sect3>
1404 <sect3>
1405 <title>Choosing the right <filename
1406 role="special">~/.hgrc</filename> file to add <literal
1407 role="rc-web">web</literal> items to</title>
1409 <para id="x_4fc">It is important to remember that a web server like
1410 Apache or <literal>lighttpd</literal> will run under a user
1411 ID that is different to yours. CGI scripts run by your
1412 server, such as <filename
1413 role="special">hgweb.cgi</filename>, will usually also run
1414 under that user ID.</para>
1416 <para id="x_4fd">If you add <literal role="rc-web">web</literal> items to
1417 your own personal <filename role="special">~/.hgrc</filename> file, CGI scripts won't read that
1418 <filename role="special">~/.hgrc</filename> file. Those
1419 settings will thus only affect the behaviour of the <command
1420 role="hg-cmd">hg serve</command> command when you run it.
1421 To cause CGI scripts to see your settings, either create a
1422 <filename role="special">~/.hgrc</filename> file in the
1423 home directory of the user ID that runs your web server, or
1424 add those settings to a system-wide <filename
1425 role="special">~/.hgrc</filename> file.</para>
1428 </sect3>
1429 </sect2>
1430 </sect1>
1431 </chapter>
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