hgbook
view en/mq.tex @ 26:1bc6c1f0192a
More MQ content.
Skeletal preface.
Skeletal preface.
| author | Bryan O'Sullivan <bos@serpentine.com> |
|---|---|
| date | Tue Jul 11 23:48:25 2006 -0700 (2006-07-11) |
| parents | 9d5b6d303ef5 |
| children | 535e87792eb1 |
line source
1 \chapter{Managing change with Mercurial Queues}
2 \label{chap:mq}
4 \section{The patch management problem}
5 \label{sec:mq:patch-mgmt}
7 Here is a common scenario: you need to install a software package from
8 source, but you find a bug that you must fix in the source before you
9 can start using the package. You make your changes, forget about the
10 package for a while, and a few months later you need to upgrade to a
11 newer version of the package. If the newer version of the package
12 still has the bug, you must extract your fix from the older source
13 tree and apply it against the newer version. This is a tedious task,
14 and it's easy to make mistakes.
16 This is a simple case of the ``patch management'' problem. You have
17 an ``upstream'' source tree that you can't change; you need to make
18 some local changes on top of the upstream tree; and you'd like to be
19 able to keep those changes separate, so that you can apply them to
20 newer versions of the upstream source.
22 The patch management problem arises in many situations. Probably the
23 most visible is that a user of an open source software project will
24 contribute a bug fix or new feature to the project's maintainers in the
25 form of a patch.
27 Distributors of operating systems that include open source software
28 often need to make changes to the packages they distribute so that
29 they will build properly in their environments.
31 When you have few changes to maintain, it is easy to manage a single
32 patch using the standard \texttt{diff} and \texttt{patch} programs
33 (see section~\ref{sec:mq:patch} for a discussion of these tools).
34 Once the number of changes grows, it starts to makes sense to maintain
35 patches as discrete ``chunks of work,'' so that for example a single
36 patch will contain only one bug fix (the patch might modify several
37 files, but it's doing ``only one thing''), and you may have a number
38 of such patches for different bugs you need fixed and local changes
39 you require. In this situation, if you submit a bug fix patch to the
40 upstream maintainers of a package and they include your fix in a
41 subsequent release, you can simply drop that single patch when you're
42 updating to the newer release.
44 Maintaining a single patch against an upstream tree is a little
45 tedious and error-prone, but not difficult. However, the complexity
46 of the problem grows rapidly as the number of patches you have to
47 maintain increases. With more than a tiny number of patches in hand,
48 understanding which ones you have applied and maintaining them moves
49 from messy to overwhelming.
51 Fortunately, Mercurial includes a powerful extension, Mercurial Queues
52 (or simply ``MQ''), that massively simplifies the patch management
53 problem.
55 \section{The prehistory of Mercurial Queues}
56 \label{sec:mq:history}
58 During the late 1990s, several Linux kernel developers started to
59 maintain ``patch series'' that modified the behaviour of the Linux
60 kernel. Some of these series were focused on stability, some on
61 feature coverage, and others were more speculative.
63 The sizes of these patch series grew rapidly. In 2002, Andrew Morton
64 published some shell scripts he had been using to automate the task of
65 managing his patch queues. Andrew was successfully using these
66 scripts to manage hundreds (sometimes thousands) of patches on top of
67 the Linux kernel.
69 \subsection{A patchwork quilt}
70 \label{sec:mq:quilt}
73 In early 2003, Andreas Gruenbacher and Martin Quinson borrowed the
74 approach of Andrew's scripts and published a tool called ``patchwork
75 quilt''~\cite{web:quilt}, or simply ``quilt''
76 (see~\cite{gruenbacher:2005} for a paper describing it). Because
77 quilt substantially automated patch management, it rapidly gained a
78 large following among open source software developers.
80 Quilt manages a \emph{stack of patches} on top of a directory tree.
81 To begin, you tell quilt to manage a directory tree; it stores away
82 the names and contents of all files in the tree. To fix a bug, you
83 create a new patch (using a single command), edit the files you need
84 to fix, then ``refresh'' the patch.
86 The refresh step causes quilt to scan the directory tree; it updates
87 the patch with all of the changes you have made. You can create
88 another patch on top of the first, which will track the changes
89 required to modify the tree from ``tree with one patch applied'' to
90 ``tree with two patches applied''.
92 You can \emph{change} which patches are applied to the tree. If you
93 ``pop'' a patch, the changes made by that patch will vanish from the
94 directory tree. Quilt remembers which patches you have popped,
95 though, so you can ``push'' a popped patch again, and the directory
96 tree will be restored to contain the modifications in the patch. Most
97 importantly, you can run the ``refresh'' command at any time, and the
98 topmost applied patch will be updated. This means that you can, at
99 any time, change both which patches are applied and what
100 modifications those patches make.
102 Quilt knows nothing about revision control tools, so it works equally
103 well on top of an unpacked tarball or a Subversion repository.
105 \subsection{From patchwork quilt to Mercurial Queues}
106 \label{sec:mq:quilt-mq}
108 In mid-2005, Chris Mason took the features of quilt and wrote an
109 extension that he called Mercurial Queues, which added quilt-like
110 behaviour to Mercurial.
112 The key difference between quilt and MQ is that quilt knows nothing
113 about revision control systems, while MQ is \emph{integrated} into
114 Mercurial. Each patch that you push is represented as a Mercurial
115 changeset. Pop a patch, and the changeset goes away.
117 This integration makes understanding patches and debugging their
118 effects \emph{enormously} easier. Since every applied patch has an
119 associated changeset, you can use \hgcmdargs{log}{\emph{filename}} to
120 see which changesets and patches affected a file. You can use the
121 \hgext{bisect} extension to binary-search through all changesets and
122 applied patches to see where a bug got introduced or fixed. You can
123 use the \hgcmd{annotate} command to see which changeset or patch
124 modified a particular line of a source file. And so on.
126 Because quilt does not care about revision control tools, it is still
127 a tremendously useful piece of software to know about for situations
128 where you cannot use Mercurial and MQ.
130 \section{Understanding patches}
131 \label{sec:mq:patch}
133 Because MQ doesn't hide its patch-oriented nature, it is helpful to
134 understand what patches are, and a little about the tools that work
135 with them.
137 The traditional Unix \command{diff} command compares two files, and
138 prints a list of differences between them. The \command{patch} command
139 understands these differences as \emph{modifications} to make to a
140 file. Take a look at figure~\ref{ex:mq:diff} for a simple example of
141 these commands in action.
143 \begin{figure}[ht]
144 \interaction{mq.diff.diff}
145 \caption{Simple uses of the \command{diff} and \command{patch} commands}
146 \label{ex:mq:diff}
147 \end{figure}
149 The type of file that \command{diff} generates (and \command{patch}
150 takes as input) is called a ``patch'' or a ``diff''; there is no
151 difference between a patch and a diff. (We'll use the term ``patch'',
152 since it's more commonly used.)
154 A patch file can start with arbitrary text; the \command{patch}
155 command ignores this text, but MQ uses it as the commit message when
156 creating changesets. To find the beginning of the patch content,
157 \command{patch} searches for the first line that starts with the
158 string ``\texttt{diff~-}''.
160 MQ works with \emph{unified} diffs (\command{patch} can accept several
161 other diff formats, but MQ doesn't). A unified diff contains two
162 kinds of header. The \emph{file header} describes the file being
163 modified; it contains the name of the file to modify. When
164 \command{patch} sees a new file header, it looks for a file with that
165 name to start modifying.
167 After the file header comes a series of \emph{hunks}. Each hunk
168 starts with a header; this identifies the range of line numbers within
169 the file that the hunk should modify. Following the header, a hunk
170 starts and ends with a few (usually three) lines of text from the
171 unmodified file; these are called the \emph{context} for the hunk. If
172 there's only a small amount of context between successive hunks,
173 \command{diff} doesn't print a new hunk header; it just runs the hunks
174 together, with a few lines of context between modifications.
176 Each line of context begins with a space character. Within the hunk,
177 a line that begins with ``\texttt{-}'' means ``remove this line,''
178 while a line that begins with ``\texttt{+}'' means ``insert this
179 line.'' For example, a line that is modified is represented by one
180 deletion and one insertion.
182 We will return to ome of the more subtle aspects of patches later (in
183 section~\ref{sec:mq:adv-patch}), but you should have enough information
184 now to use MQ.
186 \section{Getting started with Mercurial Queues}
187 \label{sec:mq:start}
189 Because MQ is implemented as an extension, you must explicitly enable
190 before you can use it. (You don't need to download anything; MQ ships
191 with the standard Mercurial distribution.) To enable MQ, edit your
192 \tildefile{.hgrc} file, and add the lines in figure~\ref{ex:mq:config}.
194 \begin{figure}[ht]
195 \begin{codesample4}
196 [extensions]
197 hgext.mq =
198 \end{codesample4}
199 \label{ex:mq:config}
200 \caption{Contents to add to \tildefile{.hgrc} to enable the MQ extension}
201 \end{figure}
203 Once the extension is enabled, it will make a number of new commands
204 available. To verify that the extension is working, you can use
205 \hgcmd{help} to see if the \hgcmd{qinit} command is now available; see
206 the example in figure~\ref{ex:mq:enabled}.
208 \begin{figure}[ht]
209 \interaction{mq.qinit-help.help}
210 \caption{How to verify that MQ is enabled}
211 \label{ex:mq:enabled}
212 \end{figure}
214 You can use MQ with \emph{any} Mercurial repository, and its commands
215 only operate within that repository. To get started, simply prepare
216 the repository using the \hgcmd{qinit} command (see
217 figure~\ref{ex:mq:qinit}). This command creates an empty directory
218 called \sdirname{.hg/patches}, where MQ will keep its metadata. As
219 with many Mercurial commands, the \hgcmd{qinit} command prints nothing
220 if it succeeds.
222 \begin{figure}[ht]
223 \interaction{mq.tutorial.qinit}
224 \caption{Preparing a repository for use with MQ}
225 \label{ex:mq:qinit}
226 \end{figure}
228 \begin{figure}[ht]
229 \interaction{mq.tutorial.qnew}
230 \caption{Creating a new patch}
231 \label{ex:mq:qnew}
232 \end{figure}
234 \subsection{Creating a new patch}
236 To begin work on a new patch, use the \hgcmd{qnew} command. This
237 command takes one argument, the name of the patch to create. MQ will
238 use this as the name of an actual file in the \sdirname{.hg/patches}
239 directory, as you can see in figure~\ref{ex:mq:qnew}.
241 Also newly present in the \sdirname{.hg/patches} directory are two
242 other files, \sfilename{series} and \sfilename{status}. The
243 \sfilename{series} file lists all of the patches that MQ knows about
244 for this repository, with one patch per line. Mercurial uses the
245 \sfilename{status} file for internal book-keeping; it tracks all of the
246 patches that MQ has \emph{applied} in this repository.
248 \begin{note}
249 You may sometimes want to edit the \sfilename{series} file by hand;
250 for example, to change the sequence in which some patches are
251 applied. However, manually editing the \sfilename{status} file is
252 almost always a bad idea, as it's easy to corrupt MQ's idea of what
253 is happening.
254 \end{note}
256 Once you have created your new patch, you can edit files in the
257 working directory as you usually would. All of the normal Mercurial
258 commands, such as \hgcmd{diff} and \hgcmd{annotate}, work exactly as
259 they did before.
261 \subsection{Refreshing a patch}
263 When you reach a point where you want to save your work, use the
264 \hgcmd{qrefresh} command (figure~\ref{ex:mq:qnew}) to update the patch
265 you are working on. This command folds the changes you have made in
266 the working directory into your patch, and updates its corresponding
267 changeset to contain those changes.
269 \begin{figure}[ht]
270 \interaction{mq.tutorial.qrefresh}
271 \caption{Refreshing a patch}
272 \label{ex:mq:qrefresh}
273 \end{figure}
275 You can run \hgcmd{qrefresh} as often as you like, so it's a good way
276 to ``checkpoint'' your work. Refresh your patch at an opportune
277 time; try an experiment; and if the experiment doesn't work out,
278 \hgcmd{revert} your modifications back to the last time you refreshed.
280 \begin{figure}[ht]
281 \interaction{mq.tutorial.qrefresh2}
282 \caption{Refresh a patch many times to accumulate changes}
283 \label{ex:mq:qrefresh2}
284 \end{figure}
286 \subsection{Stacking and tracking patches}
288 Once you have finished working on a patch, or need to work on another,
289 you can use the \hgcmd{qnew} command again to create a new patch.
290 Mercurial will apply this patch on top of your existing patch. See
291 figure~\ref{ex:mq:qnew2} for an example. Notice that the patch
292 contains the changes in our prior patch as part of its context (you
293 can see this more clearly in the output of \hgcmd{annotate}).
295 \begin{figure}[ht]
296 \interaction{mq.tutorial.qnew2}
297 \caption{Stacking a second patch on top of the first}
298 \label{ex:mq:qnew2}
299 \end{figure}
301 So far, with the exception of \hgcmd{qnew} and \hgcmd{qrefresh}, we've
302 been careful to only use regular Mercurial commands. However, there
303 are more ``natural'' commands you can use when thinking about patches
304 with MQ, as illustrated in figure~\ref{ex:mq:qseries}:
306 \begin{itemize}
307 \item The \hgcmd{qseries} command lists every patch that MQ knows
308 about in this repository, from oldest to newest (most recently
309 \emph{created}).
310 \item The \hgcmd{qapplied} command lists every patch that MQ has
311 \emph{applied} in this repository, again from oldest to newest (most
312 recently applied).
313 \end{itemize}
315 \begin{figure}[ht]
316 \interaction{mq.tutorial.qseries}
317 \caption{Understanding the patch stack with \hgcmd{qseries} and
318 \hgcmd{qapplied}}
319 \label{ex:mq:qseries}
320 \end{figure}
322 \subsection{Manipulating the patch stack}
324 The previous discussion implied that there must be a difference
325 between ``known'' and ``applied'' patches, and there is. MQ can
326 manage a patch without it being applied in the repository.
328 An \emph{applied} patch has a corresponding changeset in the
329 repository, and the effects of the patch and changeset are visible in
330 the working directory. You can undo the application of a patch using
331 the \hgcmd{qpop} command. MQ still \emph{knows about}, or manages, a
332 popped patch, but the patch no longer has a corresponding changeset in
333 the repository, and the working directory does not contain the changes
334 made by the patch. Figure~\ref{fig:mq:stack} illustrates the
335 difference between applied and tracked patches.
337 \begin{figure}[ht]
338 \centering
339 \grafix{mq-stack}
340 \caption{Applied and unapplied patches in the MQ patch stack}
341 \label{fig:mq:stack}
342 \end{figure}
344 You can reapply an unapplied, or popped, patch using the \hgcmd{qpush}
345 command. This creates a new changeset to correspond to the patch, and
346 the patch's changes once again become present in the working
347 directory. See figure~\ref{ex:mq:qpop} for examples of \hgcmd{qpop}
348 and \hgcmd{qpush} in action. Notice that once we have popped a patch
349 or two patches, the output of \hgcmd{qseries} remains the same, while
350 that of \hgcmd{qapplied} has changed.
352 \begin{figure}[ht]
353 \interaction{mq.tutorial.qpop}
354 \caption{Modifying the stack of applied patches}
355 \label{ex:mq:qpop}
356 \end{figure}
358 MQ does not limit you to pushing or popping one patch. You can have
359 no patches, all of them, or any number in between applied at some
360 point in time.
362 \subsection{Working on several patches at once}
364 The \hgcmd{qrefresh} command always refreshes the \emph{topmost}
365 applied patch. This means that you can suspend work on one patch (by
366 refreshing it), pop or push to make a different patch the top, and
367 work on \emph{that} patch for a while.
369 Here's an example that illustrates how you can use this ability.
370 Let's say you're developing a new feature as two patches. The first
371 is a change to the core of your software, and the second---layered on
372 top of the first---changes the user interface to use the code you just
373 added to the core. If you notice a bug in the core while you're
374 working on the UI patch, it's easy to fix the core. Simply
375 \hgcmd{qrefresh} the UI patch to save your in-progress changes, and
376 \hgcmd{qpop} down to the core patch. Fix the core bug,
377 \hgcmd{qrefresh} the core patch, and \hgcmd{qpush} back to the UI
378 patch to continue where you left off.
380 \section{More about patches}
381 \label{sec:mq:adv-patch}
383 MQ uses the GNU \command{patch} command to apply patches, so it's
384 helpful to know a few more detailed aspects of how \command{patch}
385 works, and about patches themselves.
387 \subsection{The strip count}
389 If you look at the file headers in a patch, you will notice that the
390 pathnames usually have an extra component on the front that isn't
391 present in the actual path name. This is a holdover from the way that
392 people used to generate patches (people still do this, but it's
393 somewhat rare with modern revision control tools).
395 Alice would unpack a tarball, edit her files, then decide that she
396 wanted to create a patch. So she'd rename her working directory,
397 unpack the tarball again (hence the need for the rename), and use the
398 \cmdopt{diff}{-r} and \cmdopt{diff}{-N} options to \command{diff} to
399 recursively generate a patch between the unmodified directory and the
400 modified one. The result would be that the name of the unmodified
401 directory would be at the front of the left-hand path in every file
402 header, and the name of the modified directory would be at the front
403 of the right-hand path.
405 Since someone receiving a patch from the Alices of the net would be
406 unlikely to have unmodified and modified directories with exactly the
407 same names, the \command{patch} command has a \cmdopt{patch}{-p}
408 option that indicates the number of leading path name components to
409 strip when trying to apply a patch. This number is called the
410 \emph{strip count}.
412 An option of ``\texttt{-p1}'' means ``use a strip count of one''. If
413 \command{patch} sees a file name \filename{foo/bar/baz} in a file
414 header, it will strip \filename{foo} and try to patch a file named
415 \filename{bar/baz}. (Strictly speaking, the strip count refers to the
416 number of \emph{path separators} (and the components that go with them
417 ) to strip. A strip count of one will turn \filename{foo/bar} into
418 \filename{bar}, but \filename{/foo/bar} (notice the extra leading
419 slash) into \filename{foo/bar}.)
421 The ``standard'' strip count for patches is one; almost all patches
422 contain one leading path name component that needs to be stripped.
423 Mercurial's \hgcmd{diff} command generates path names in this form,
424 and the \hgcmd{import} command and MQ expect patches to have a strip
425 count of one.
427 If you receive a patch from someone that you want to add to your patch
428 queue, and the patch needs a strip count other than one, you cannot
429 just \hgcmd{qimport} the patch, because \hgcmd{qimport} does not yet
430 have a \texttt{-p} option (see~\bug{311}). Your best bet is to
431 \hgcmd{qnew} a patch of your own, then use \cmdargs{patch}{-p\emph{N}}
432 to apply their patch, followed by \hgcmd{addremove} to pick up any
433 files added or removed by the patch, followed by \hgcmd{qrefresh}.
434 This complexity may become unnecessary; see~\bug{311} for details.
435 \subsection{Strategies for applying a patch}
437 When \command{patch} applies a hunk, it tries a handful of
438 successively less accurate strategies to try to make the hunk apply.
439 This falling-back technique often makes it possible to take a patch
440 that was generated against an old version of a file, and apply it
441 against a newer version of that file.
443 First, \command{patch} tries an exact match, where the line numbers,
444 the context, and the text to be modified must apply exactly. If it
445 cannot make an exact match, it tries to find an exact match for the
446 context, without honouring the line numbering information. If this
447 succeeds, it prints a line of output saying that the hunk was applied,
448 but at some \emph{offset} from the original line number.
450 If a context-only match fails, \command{patch} removes the first and
451 last lines of the context, and tries a \emph{reduced} context-only
452 match. If the hunk with reduced context succeeds, it prints a message
453 saying that it applied the hunk with a \emph{fuzz factor} (the number
454 after the fuzz factor indicates how many lines of context
455 \command{patch} had to trim before the patch applied).
457 When neither of these techniques works, \command{patch} prints a
458 message saying that the hunk in question was rejected. It saves
459 rejected hunks (also simply called ``rejects'') to a file with the
460 same name, and an added \sfilename{.rej} extension. It also saves an
461 unmodified copy of the file with a \sfilename{.orig} extension; the
462 copy of the file without any extensions will contain any changes made
463 by hunks that \emph{did} apply cleanly. If you have a patch that
464 modifies \filename{foo} with six hunks, and one of them fails to
465 apply, you will have: an unmodified \filename{foo.orig}, a
466 \filename{foo.rej} containing one hunk, and \filename{foo}, containing
467 the changes made by the five successful five hunks.
469 \subsection{Some quirks of patch representation}
471 There are a few useful things to know about how \command{patch} works
472 with files.
473 \begin{itemize}
474 \item This should already be obvious, but \command{patch} cannot
475 handle binary files.
476 \item Neither does it care about the executable bit; it creates new
477 files as readable, but not executable.
478 \item \command{patch} treats the removal of a file as a diff between
479 the file to be removed and the empty file. So your idea of ``I
480 deleted this file'' looks like ``every line of this file was
481 deleted'' in a patch.
482 \item It treats the addition of a file as a diff between the empty
483 file and the file to be added. So in a patch, your idea of ``I
484 added this file'' looks like ``every line of this file was added''.
485 \item It treats a renamed file as the removal of the old name, and the
486 addition of the new name. This means that renamed files have a big
487 footprint in patches. (Note also that Mercurial does not currently
488 try to infer when files have been renamed or copied in a patch.)
489 \item \command{patch} cannot represent empty files, so you cannot use
490 a patch to represent the notion ``I added this empty file to the
491 tree''.
492 \end{itemize}
493 \subsection{Beware the fuzz}
495 While applying a hunk at an offset, or with a fuzz factor, will often
496 be completely successful, these inexact techniques naturally leave
497 open the possibility of corrupting the patched file. The most common
498 cases typically involve applying a patch twice, or at an incorrect
499 location in the file. If \command{patch} or \hgcmd{qpush} ever
500 mentions an offset or fuzz factor, you should make sure that the
501 modified files are correct afterwards.
503 It's often a good idea to refresh a patch that has applied with an
504 offset or fuzz factor; refreshing the patch generates new context
505 information that will make it apply cleanly. I say ``often,'' not
506 ``always,'' because sometimes refreshing a patch will make it fail to
507 apply against a different revision of the underlying files. In some
508 cases, such as when you're maintaining a patch that must sit on top of
509 multiple versions of a source tree, it's acceptable to have a patch
510 apply with some fuzz, provided you've verified the results of the
511 patching process in such cases.
513 \subsection{Handling rejection}
515 If \hgcmd{qpush} fails to apply a patch, it will print an error
516 message and exit. If it has left \sfilename{.rej} files behind, it is
517 usually best to fix up the rejected hunks before you push more patches
518 or do any further work.
520 If your patch \emph{used to} apply cleanly, and no longer does because
521 you've changed the underlying code that your patches are based on,
522 Mercurial Queues can help; see section~\ref{sec:mq:merge} for details.
524 Unfortunately, there aren't any great techniques for dealing with
525 rejected hunks. Most often, you'll need to view the \sfilename{.rej}
526 file and edit the target file, applying the rejected hunks by hand.
528 If you're feeling adventurous, Neil Brown, a Linux kernel hacker,
529 wrote a tool called \command{wiggle}~\cite{web:wiggle}, which is more
530 vigorous than \command{patch} in its attempts to make a patch apply.
532 Another Linux kernel hacker, Chris Mason (the author of Mercurial
533 Queues), wrote a similar tool called \command{rej}~\cite{web:rej},
534 which takes a simple approach to automating the application of hunks
535 rejected by \command{patch}. \command{rej} can help with four common
536 reasons that a hunk may be rejected:
538 \begin{itemize}
539 \item The context in the middle of a hunk has changed.
540 \item A hunk is missing some context at the beginning or end.
541 \item A large hunk might apply better---either entirely or in
542 part---if it was broken up into smaller hunks.
543 \item A hunk removes lines with slightly different content than those
544 currently present in the file.
545 \end{itemize}
547 If you use \command{wiggle} or \command{rej}, you should be doubly
548 careful to check your results when you're done.
550 \section{Getting the best performance out of MQ}
552 MQ is very efficient at handling a large number of patches. I ran
553 some performance experiments in mid-2006 for a talk that I gave at the
554 2006 EuroPython conference~\cite{web:europython}. I used as my data
555 set the Linux 2.6.17-mm1 patch series, which consists of 1,738
556 patches. I applied thes on top of a Linux kernel repository
557 containing all 27,472 revisions between Linux 2.6.12-rc2 and Linux
558 2.6.17.
560 On my old, slow laptop, I was able to
561 \hgcmdargs{qpush}{\hgopt{qpush}{-a}} all 1,738 patches in 3.5 minutes,
562 and \hgcmdargs{qpop}{\hgopt{qpop}{-a}} them all in 30 seconds. I
563 could \hgcmd{qrefresh} one of the biggest patches (which made 22,779
564 lines of changes to 287 files) in 6.6 seconds.
566 Clearly, MQ is well suited to working in large trees, but there are a
567 few tricks you can use to get the best performance of it.
569 First of all, try to ``batch'' operations together. Every time you
570 run \hgcmd{qpush} or \hgcmd{qpop}, these commands scan the working
571 directory once to make sure you haven't made some changes and then
572 forgotten to run \hgcmd{qrefresh}. On a small tree, the time that
573 this scan takes is unnoticeable. However, on a medium-sized tree
574 (containing tens of thousands of files), it can take a second or more.
576 The \hgcmd{qpush} and \hgcmd{qpop} commands allow you to push and pop
577 multiple patches at a time. You can identify the ``destination
578 patch'' that you want to end up at. When you \hgcmd{qpush} with a
579 destination specified, it will push patches until that patch is at the
580 top of the applied stack. When you \hgcmd{qpop} to a destination, MQ
581 will pop patches until the destination patch \emph{is no longer}
582 applied.
584 You can identify a destination patch using either the name of the
585 patch, or by number. If you use numeric addressing, patches are
586 counted from zero; this means that the first patch is zero, the second
587 is one, and so on.
589 \section{Updating your patches when the underlying code changes}
590 \label{sec:mq:merge}
592 It's common to have a stack of patches on top of an underlying
593 repository that you don't modify directly. If you're working on
594 changes to third-party code, or on a feature that is taking longer to
595 develop than the rate of change of the code beneath, you will often
596 need to sync up with the underlying code, and fix up any hunks in your
597 patches that no longer apply. This is called \emph{rebasing} your
598 patch series.
600 The simplest way to do this is to \hgcmdargs{qpop}{\hgopt{qpop}{-a}}
601 your patches, then \hgcmd{pull} changes into the underlying
602 repository, and finally \hgcmdargs{qpush}{\hgopt{qpop}{-a}} your
603 patches again. MQ will stop pushing any time it runs across a patch
604 that fails to apply during conflicts, allowing you to fix your
605 conflicts, \hgcmd{qrefresh} the affected patch, and continue pushing
606 until you have fixed your entire stack.
608 This approach is easy to use and works well if you don't expect
609 changes to the underlying code to affect how well your patches apply.
610 If your patch stack touches code that is modified frequently or
611 invasively in the underlying repository, however, fixing up rejected
612 hunks by hand quickly becomes tiresome.
614 It's possible to partially automate the rebasing process. If your
615 patches apply cleanly against some revision of the underlying repo, MQ
616 can use this information to help you to resolve conflicts between your
617 patches and a different revision.
619 The process is a little involved.
620 \begin{enumerate}
621 \item To begin, \hgcmdargs{qpush}{-a} all of your patches on top of
622 the revision where you know that they apply cleanly.
623 \item Save a backup copy of your patch directory using
624 \hgcmdargs{qsave}{\hgopt{qsave}{-e} \hgopt{qsave}{-c}}. This prints
625 the name of the directory that it has saved the patches in. It will
626 save the patches to a directory called
627 \sdirname{.hg/patches.\emph{N}}, where \texttt{\emph{N}} is a small
628 integer. It also commits a ``save changeset'' on top of your
629 applied patches; this is for internal book-keeping, and records the
630 states of the \sfilename{series} and \sfilename{status} files.
631 \item Use \hgcmd{pull} to bring new changes into the underlying
632 repository. (Don't run \hgcmdargs{pull}{-u}; see below for why.)
633 \item Update to the new tip revision, using
634 \hgcmdargs{update}{\hgopt{update}{-C}} to override the patches you
635 have pushed.
636 \item Merge all patches using \hgcmdargs{qpush}{\hgopt{qpush}{-m}
637 \hgopt{qpush}{-a}}. The \hgopt{qpush}{-m} option to \hgcmd{qpush}
638 tells MQ to perform a three-way merge if the patch fails to apply.
639 \end{enumerate}
641 During the \hgcmdargs{qpush}{\hgopt{qpush}{-m}}, each patch in the
642 \sfilename{series} file is applied normally. If a patch applies with
643 fuzz or rejects, MQ looks at the queue you \hgcmd{qsave}d, and
644 performs a three-way merge with the corresponding changeset. This
645 merge uses Mercurial's normal merge machinery, so it may pop up a GUI
646 merge tool to help you to resolve problems.
648 When you finish resolving the effects of a patch, MQ refreshes your
649 patch based on the result of the merge.
651 At the end of this process, your repository will have one extra head
652 from the old patch queue, and a copy of the old patch queue will be in
653 \sdirname{.hg/patches.\emph{N}}. You can remove the extra head using
654 \hgcmdargs{qpop}{\hgopt{qpop}{-a} \hgopt{qpop}{-n} patches.\emph{N}}
655 or \hgcmd{strip}. You can delete \sdirname{.hg/patches.\emph{N}} once
656 you are sure that you no longer need it as a backup.
658 \section{Useful things to know about}
660 There are a number of aspects of MQ usage that don't fit tidily into
661 sections of their own, but that are good to know. Here they are, in
662 one place.
664 \begin{itemize}
665 \item Normally, when you \hgcmd{qpop} a patch and \hgcmd{qpush} it
666 again, the changeset that represents the patch after the pop/push
667 will have a \emph{different identity} than the changeset that
668 represented the hash beforehand. See section~\ref{sec:mq:cmd:qpush}
669 for information as to why this is.
670 \item It's not a good idea to \hgcmd{merge} changes from another
671 branch with a patch changeset, at least if you want to maintain the
672 ``patchiness'' of that changeset and changesets below it on the
673 patch stack. If you try to do this, it will appear to succeed, but
674 MQ will become confused.
675 \end{itemize}
676 \section{Managing patches in a repository}
678 Because MQ's \sdirname{.hg/patches} directory resides outside a
679 Mercurial repository's working directory, the ``underlying'' Mercurial
680 repository knows nothing about the management or presence of patches.
682 This presents the interesting possibility of managing the contents of
683 the patch directory as a Mercurial repository in its own right. This
684 can be a useful way to work. For example, you can work on a patch for
685 a while, \hgcmd{qrefresh} it, then \hgcmd{commit} the current state of
686 the patch. This lets you ``roll back'' to that version of the patch
687 later on.
689 You can then share different versions of the same patch stack among
690 multiple underlying repositories. I use this when I am developing a
691 Linux kernel feature. I have a pristine copy of my kernel sources for
692 each of several CPU architectures, and a cloned repository under each
693 that contains the patches I am working on. When I want to test a
694 change on a different architecture, I push my current patches to the
695 patch repository associated with that kernel tree, pop and push all of
696 my patches, and build and test that kernel.
698 Managing patches in a repository makes it possible for multiple
699 developers to work on the same patch series without colliding with
700 each other, all on top of an underlying source base that they may or
701 may not control.
703 \subsection{MQ support for patch repositories}
705 MQ helps you to work with the \sdirname{.hg/patches} directory as a
706 repository; when you prepare a repository for working with patches
707 using \hgcmd{qinit}, you can pass the \hgopt{qinit}{-c} option to
708 create the \sdirname{.hg/patches} directory as a Mercurial repository.
710 \begin{note}
711 If you forget to use the \hgopt{qinit}{-c} option, you can simply go
712 into the \sdirname{.hg/patches} directory at any time and run
713 \hgcmd{init}. Don't forget to add an entry for the
714 \sfilename{status} file to the \sfilename{.hgignore} file, though
715 (\hgcmdargs{qinit}{\hgopt{qinit}{-c}} does this for you
716 automatically); you \emph{really} don't want to manage the
717 \sfilename{status} file.
718 \end{note}
720 As a convenience, if MQ notices that the \dirname{.hg/patches}
721 directory is a repository, it will automatically \hgcmd{add} every
722 patch that you create and import.
724 Finally, MQ provides a shortcut command, \hgcmd{qcommit}, that runs
725 \hgcmd{commit} in the \sdirname{.hg/patches} directory. This saves
726 some cumbersome typing.
728 \subsection{A few things to watch out for}
730 MQ's support for working with a repository full of patches is limited
731 in a few small respects.
733 MQ cannot automatically detect changes that you make to the patch
734 directory. If you \hgcmd{pull}, manually edit, or \hgcmd{update}
735 changes to patches or the \sfilename{series} file, you will have to
736 \hgcmdargs{qpop}{\hgopt{qpop}{-a}} and then
737 \hgcmdargs{qpush}{\hgopt{qpush}{-a}} in the underlying repository to
738 see those changes show up there. If you forget to do this, you can
739 confuse MQ's idea of which patches are applied.
741 \section{Third party tools for working with patches}
742 \label{sec:mq:tools}
744 Once you've been working with patches for a while, you'll find
745 yourself hungry for tools that will help you to understand and
746 manipulate the patches you're dealing with.
748 The \command{diffstat} command~\cite{web:diffstat} generates a
749 histogram of the modifications made to each file in a patch. It
750 provides a good way to ``get a sense of'' a patch---which files it
751 affects, and how much change it introduces to each file and as a
752 whole. (I find that it's a good idea to use \command{diffstat}'s
753 \texttt{-p} option as a matter of course, as otherwise it will try to
754 do clever things with prefixes of file names that inevitably confuse
755 at least me.)
757 \begin{figure}[ht]
758 \interaction{mq.tools.tools}
759 \caption{The \command{diffstat}, \command{filterdiff}, and \command{lsdiff} commands}
760 \label{ex:mq:tools}
761 \end{figure}
763 The \package{patchutils} package~\cite{web:patchutils} is invaluable.
764 It provides a set of small utilities that follow the ``Unix
765 philosophy;'' each does one useful thing with a patch. The
766 \package{patchutils} command I use most is \command{filterdiff}, which
767 extracts subsets from a patch file. For example, given a patch that
768 modifies hundreds of files across dozens of directories, a single
769 invocation of \command{filterdiff} can generate a smaller patch that
770 only touches files whose names match a particular glob pattern.
772 \section{Good ways to work with patches}
774 Whether you are working on a patch series to submit to a free software
775 or open source project, or a series that you intend to treat as a
776 sequence of regular changesets when you're done, you can use some
777 simple techniques to keep your work well organised.
779 Give your patches descriptive names. A good name for a patch might be
780 \filename{rework-device-alloc.patch}, because it will immediately give
781 you a hint what the purpose of the patch is. Long names shouldn't be
782 a problem; you won't be typing the names often, but you \emph{will} be
783 running commands like \hgcmd{qapplied} and \hgcmd{qtop} over and over.
784 Good naming becomes especially important when you have a number of
785 patches to work with, or if you are juggling a number of different
786 tasks and your patches only get a fraction of your attention.
788 Be aware of what patch you're working on. Use the \hgcmd{qtop}
789 command and skim over the text of your patches frequently---for
790 example, using \hgcmdargs{tip}{\hgopt{tip}{-p}})---to be sure of where
791 you stand. I have several times worked on and \hgcmd{qrefresh}ed a
792 patch other than the one I intended, and it's often tricky to migrate
793 changes into the right patch after making them in the wrong one.
795 For this reason, it is very much worth investing a little time to
796 learn how to use some of the third-party tools I described in
797 section~\ref{sec:mq:tools}, particularly \command{diffstat} and
798 \command{filterdiff}. The former will give you a quick idea of what
799 changes your patch is making, while the latter makes it easy to splice
800 hunks selectively out of one patch and into another.
802 \section{MQ cookbook}
804 \subsection{Manage ``trivial'' patches}
806 Because the overhead of dropping files into a new Mercurial repository
807 is so low, it makes a lot of sense to manage patches this way even if
808 you simply want to make a few changes to a source tarball that you
809 downloaded.
811 Begin by downloading and unpacking the source tarball,
812 and turning it into a Mercurial repository.
813 \interaction{mq.tarball.download}
815 Continue by creating a patch stack and making your changes.
816 \interaction{mq.tarball.qinit}
818 Let's say a few weeks or months pass, and your package author releases
819 a new version. First, bring their changes into the repository.
820 \interaction{mq.tarball.newsource}
821 The pipeline starting with \hgcmd{locate} above deletes all files in
822 the working directory, so that \hgcmd{commit}'s
823 \hgopt{commit}{--addremove} option can actually tell which files have
824 really been removed in the newer version of the source.
826 Finally, you can apply your patches on top of the new tree.
827 \interaction{mq.tarball.repush}
829 \subsection{Combining entire patches}
830 \label{sec:mq:combine}
832 It's easy to combine entire patches.
834 \begin{enumerate}
835 \item \hgcmd{qpop} your applied patches until neither patch is
836 applied.
837 \item Concatenate the patches that you want to combine together:
838 \begin{codesample4}
839 cat patch-to-drop.patch >> patch-to-augment.patch
840 \end{codesample4}
841 The description from the first patch (if you have one) will be used
842 as the commit comment when you \hgcmd{qpush} the combined patch.
843 Edit the patch description if you need to.
844 \item Use the \hgcmd{qdel} command to delete the patch you're dropping
845 from the \sfilename{series} file.
846 \item \hgcmd{qpush} the combined patch. Fix up any rejects.
847 \item \hgcmd{qrefresh} the combined patch to tidy it up.
848 \end{enumerate}
850 \subsection{Merging part of one patch into another}
852 Merging \emph{part} of one patch into another is more difficult than
853 combining entire patches.
855 If you want to move changes to entire files, you can use
856 \command{filterdiff}'s \cmdopt{filterdiff}{-i} and
857 \cmdopt{filterdiff}{-x} options to choose the modifications to snip
858 out of one patch, concatenating its output onto the end of the patch
859 you want to merge into. You usually won't need to modify the patch
860 you've merged the changes from. Instead, MQ will report some rejected
861 hunks when you \hgcmd{qpush} it (from the hunks you moved into the
862 other patch), and you can simply \hgcmd{qrefresh} the patch to drop
863 the duplicate hunks.
865 If you have a patch that has multiple hunks modifying a file, and you
866 only want to move a few of those hunks, the job becomes more messy,
867 but you can still partly automate it. Use \cmdargs{lsdiff}{-nvv} to
868 print some metadata about the patch.
869 \interaction{mq.tools.lsdiff}
871 This command prints three different kinds of number:
872 \begin{itemize}
873 \item (in the first column) a \emph{file number} to identify each file
874 modified in the patch;
875 \item (on the next line, indented) the line number within a modified
876 file where a hunk starts; and
877 \item (on the same line) a \emph{hunk number} to identify that hunk.
878 \end{itemize}
880 You'll have to use some visual inspection, and reading of the patch,
881 to identify the file and hunk numbers you'll want, but you can then
882 pass them to to \command{filterdiff}'s \cmdopt{filterdiff}{--files}
883 and \cmdopt{filterdiff}{--hunks} options, to select exactly the file
884 and hunk you want to extract.
886 Once you have this hunk, you can concatenate it onto the end of your
887 destination patch and continue with the remainder of
888 section~\ref{sec:mq:combine}.
890 \section{Differences between quilt and MQ}
892 If you are already familiar with quilt, MQ provides a similar command
893 set. There are a few differences in the way that it works.
895 You will already have noticed that most quilt commands have MQ
896 counterparts that simply begin with a ``\texttt{q}''. The exceptions
897 are quilt's \texttt{add} and \texttt{remove} commands, the
898 counterparts for which are the normal Mercurial \hgcmd{add} and
899 \hgcmd{remove} commands. There is no MQ equivalent of the quilt
900 \texttt{edit} command.
901 \section{MQ command reference}
902 \label{sec:mq:cmdref}
904 For an overview of the commands provided by MQ, use the command
905 \hgcmdargs{help}{mq}.
907 \subsection{\hgcmd{qapplied}---print applied patches}
909 The \hgcmd{qapplied} command prints the current stack of applied
910 patches. Patches are printed in oldest-to-newest order, so the last
911 patch in the list is the ``top'' patch.
913 \subsection{\hgcmd{qcommit}---commit changes in the queue repository}
915 The \hgcmd{qcommit} command commits any outstanding changes in the
916 \sdirname{.hg/patches} repository. This command only works if the
917 \sdirname{.hg/patches} directory is a repository, i.e.~you created the
918 directory using \hgcmdargs{qinit}{\hgopt{qinit}{-c}} or ran
919 \hgcmd{init} in the directory after running \hgcmd{qinit}.
921 This command is shorthand for \hgcmdargs{commit}{--cwd .hg/patches}.
923 \subsection{\hgcmd{qdelete}---delete a patch from the
924 \sfilename{series} file}
926 The \hgcmd{qdelete} command removes the entry for a patch from the
927 \sfilename{series} file in the \sdirname{.hg/patches} directory. It
928 does not delete the patch file, nor does it pop the patch if the patch
929 is already applied.
931 \subsection{\hgcmd{qdiff}---print a diff of the topmost applied patch}
933 The \hgcmd{qdiff} command prints a diff of the topmost applied patch.
934 It is equivalent to \hgcmdargs{diff}{-r-2:-1}.
936 \subsection{\hgcmd{qimport}---import a third-party patch into the queue}
938 The \hgcmd{qimport} command adds an entry for an external patch to the
939 \sfilename{series} file, and copies the patch into the
940 \sdirname{.hg/patches} directory. It adds the entry immediately after
941 the topmost applied patch, but does not push the patch.
943 If the \sdirname{.hg/patches} directory is a repository,
944 \hgcmd{qimport} automatically does an \hgcmd{add} of the imported
945 patch.
947 \subsection{\hgcmd{qinit}---prepare a repository to work with MQ}
949 The \hgcmd{qinit} command prepares a repository to work with MQ. It
950 creates a directory called \sdirname{.hg/patches}.
952 Options:
953 \begin{itemize}
954 \item[\hgopt{qinit}{-c}] Create \sdirname{.hg/patches} as a repository
955 in its own right. Also creates a \sfilename{.hgignore} file that
956 will ignore the \sfilename{status} file.
957 \end{itemize}
959 When the \sdirname{.hg/patches} directory is a repository, the
960 \hgcmd{qimport} and \hgcmd{qnew} commands automatically \hgcmd{add}
961 new patches.
963 \subsection{\hgcmd{qnew}---create a new patch}
965 The \hgcmd{qnew} command creates a new patch. It takes one mandatory
966 argument, the name to use for the patch file. The newly created patch
967 is created empty by default. It is added to the \sfilename{series}
968 file after the current topmost applied patch, and is immediately
969 pushed on top of that patch.
971 If \hgcmd{qnew} finds modified files in the working directory, it will
972 refuse to create a new patch unless the \hgopt{qnew}{-f} option is
973 used (see below). This behaviour allows you to \hgcmd{qrefresh} your
974 topmost applied patch before you apply a new patch on top of it.
976 Options:
977 \begin{itemize}
978 \item[\hgopt{qnew}{-f}] Create a new patch if the contents of the
979 working directory are modified. Any outstanding modifications are
980 added to the newly created patch, so after this command completes,
981 the working directory will no longer be modified.
982 \item[\hgopt{qnew}{-m}] Use the given text as the commit message.
983 This text will be stored at the beginning of the patch file, before
984 the patch data.
985 \end{itemize}
987 \subsection{\hgcmd{qnext}---print the name of the next patch}
989 The \hgcmd{qnext} command prints the name name of the next patch in
990 the \sfilename{series} file after the topmost applied patch. This
991 patch will become the topmost applied patch if you run \hgcmd{qpush}.
993 \subsection{\hgcmd{qpop}---pop patches off the stack}
995 The \hgcmd{qpop} command removes applied patches from the top of the
996 stack of applied patches. By default, it removes only one patch.
998 This command removes the changesets that represent the popped patches
999 from the repository, and updates the working directory to undo the
1000 effects of the patches.
1002 This command takes an optional argument, which it uses as the name or
1003 index of the patch to pop to. If given a name, it will pop patches
1004 until the named patch is no longer applied. If given a number,
1005 \hgcmd{qpop} treats the number as an index into the entries in the
1006 series file, counting from zero (empty lines and lines containing only
1007 comments do not count). It pops patches until the patch identified by
1008 the given index is no longer applied.
1010 The \hgcmd{qpop} command does not read or write patches or the
1011 \sfilename{series} file. It is thus safe to \hgcmd{qpop} a patch that
1012 you have removed from the \sfilename{series} file, or a patch that you
1013 have renamed or deleted entirely. In the latter two cases, use the
1014 name of the patch as it was when you applied it.
1016 By default, the \hgcmd{qpop} command will not pop any patches if the
1017 working directory has been modified. You can override this behaviour
1018 using the \hgopt{qpop}{-f} option, which reverts all modifications in
1019 the working directory.
1021 Options:
1022 \begin{itemize}
1023 \item[\hgopt{qpop}{-a}] Pop all applied patches. This returns the
1024 repository to its state before you applied any patches.
1025 \item[\hgopt{qpop}{-f}] Forcibly revert any modifications to the
1026 working directory when popping.
1027 \item[\hgopt{qpop}{-n}] Pop a patch from the named queue.
1028 \end{itemize}
1030 The \hgcmd{qpop} command removes one line from the end of the
1031 \sfilename{status} file for each patch that it pops.
1032 \subsection{\hgcmd{qprev}---print the name of the previous patch}
1034 The \hgcmd{qprev} command prints the name of the patch in the
1035 \sfilename{series} file that comes before the topmost applied patch.
1036 This will become the topmost applied patch if you run \hgcmd{qpop}.
1038 \subsection{\hgcmd{qpush}---push patches onto the stack}
1039 \label{sec:mq:cmd:qpush}
1041 The \hgcmd{qpush} command adds patches onto the applied stack. By
1042 default, it adds only one patch.
1044 This command creates a new changeset to represent each applied patch,
1045 and updates the working directory to apply the effects of the patches.
1047 The default data used when creating a changeset are as follows:
1048 \begin{itemize}
1049 \item The commit date and time zone are the current date and time
1050 zone. Because these data are used to compute the identity of a
1051 changeset, this means that if you \hgcmd{qpop} a patch and
1052 \hgcmd{qpush} it again, the changeset that you push will have a
1053 different identity than the changeset you popped.
1054 \item The author is the same as the default used by the \hgcmd{commit}
1055 command.
1056 \item The commit message is any text from the patch file that comes
1057 before the first diff header. If there is no such text, a default
1058 commit message is used that identifies the name of the patch.
1059 \end{itemize}
1060 If a patch contains a Mercurial patch header (XXX add link), the
1061 information in the patch header overrides these defaults.
1063 Options:
1064 \begin{itemize}
1065 \item[\hgopt{qpush}{-a}] Push all unapplied patches from the
1066 \sfilename{series} file until there are none left to push.
1067 \item[\hgopt{qpush}{-l}] Add the name of the patch to the end
1068 of the commit message.
1069 \item[\hgopt{qpush}{-m}] If a patch fails to apply cleanly, use the
1070 entry for the patch in another saved queue to compute the parameters
1071 for a three-way merge, and perform a three-way merge using the
1072 normal Mercurial merge machinery. Use the resolution of the merge
1073 as the new patch content.
1074 \item[\hgopt{qpush}{-n}] Use the named queue if merging while pushing.
1075 \end{itemize}
1077 The \hgcmd{qpush} command reads, but does not modify, the
1078 \sfilename{series} file. It appends one line to the \hgcmd{status}
1079 file for each patch that it pushes.
1081 \subsection{\hgcmd{qrefresh}---update the topmost applied patch}
1083 The \hgcmd{qrefresh} command updates the topmost applied patch. It
1084 modifies the patch, removes the old changeset that represented the
1085 patch, and creates a new changeset to represent the modified patch.
1087 The \hgcmd{qrefresh} command looks for the following modifications:
1088 \begin{itemize}
1089 \item Changes to the commit message, i.e.~the text before the first
1090 diff header in the patch file, are reflected in the new changeset
1091 that represents the patch.
1092 \item Modifications to tracked files in the working directory are
1093 added to the patch.
1094 \item Changes to the files tracked using \hgcmd{add}, \hgcmd{copy},
1095 \hgcmd{remove}, or \hgcmd{rename}. Added files and copy and rename
1096 destinations are added to the patch, while removed files and rename
1097 sources are removed.
1098 \end{itemize}
1100 Even if \hgcmd{qrefresh} detects no changes, it still recreates the
1101 changeset that represents the patch. This causes the identity of the
1102 changeset to differ from the previous changeset that identified the
1103 patch.
1105 \subsection{\hgcmd{qrestore}---restore saved queue state}
1107 XXX No idea what this does.
1109 \subsection{\hgcmd{qsave}---save current queue state}
1111 XXX Likewise.
1113 \subsection{\hgcmd{qseries}---print the entire patch series}
1115 The \hgcmd{qseries} command prints the entire patch series from the
1116 \sfilename{series} file. It prints only patch names, not empty lines
1117 or comments. It prints in order from first to be applied to last.
1119 \subsection{\hgcmd{qtop}---print the name of the current patch}
1121 The \hgcmd{qtop} prints the name of the topmost currently applied
1122 patch.
1124 \subsection{\hgcmd{qunapplied}---print patches not yet applied}
1126 The \hgcmd{qunapplied} command prints the names of patches from the
1127 \sfilename{series} file that are not yet applied. It prints them in
1128 order from the next patch that will be pushed to the last.
1130 \subsection{\hgcmd{qversion}}
1132 The \hgcmd{qversion} command prints the version of MQ that is in use.
1134 \subsection{\hgcmd{strip}---remove a revision and descendants}
1136 The \hgcmd{strip} command removes a revision, and all of its
1137 descendants, from the repository. It undoes the effects of the
1138 removed revisions from the repository, and updates the working
1139 directory to the first parent of the removed revision.
1141 The \hgcmd{strip} command saves a backup of the removed changesets in
1142 a bundle, so that they can be reapplied if removed in error.
1144 Options:
1145 \begin{itemize}
1146 \item[\hgopt{strip}{-b}] Save unrelated changesets that are intermixed
1147 with the stripped changesets in the backup bundle.
1148 \item[\hgopt{strip}{-f}] If a branch has multiple heads, remove all
1149 heads. XXX This should be renamed, and use \texttt{-f} to strip revs
1150 when there are pending changes.
1151 \item[\hgopt{strip}{-n}] Do not save a backup bundle.
1152 \end{itemize}
1153 \section{MQ file reference}
1156 \subsection{The \sfilename{series} file}
1158 The \sfilename{series} file contains a list of the names of all
1159 patches that MQ can apply. It is represented as a list of names, with
1160 one name saved per line. Leading and trailing white space in each
1161 line are ignored.
1163 Lines may contain comments. A comment begins with the ``\texttt{\#}''
1164 character, and extends to the end of the line. Empty lines, and lines
1165 that contain only comments, are ignored.
1167 You will often need to edit the \sfilename{series} file by hand, hence
1168 the support for comments and empty lines noted above. For example,
1169 you can comment out a patch temporarily, and \hgcmd{qpush} will skip
1170 over that patch when applying patches. You can also change the order
1171 in which patches are applied by reordering their entries in the
1172 \sfilename{series} file.
1174 Placing the \sfilename{series} file under revision control is also
1175 supported; it is a good idea to place all of the patches that it
1176 refers to under revision control, as well. If you create a patch
1177 directory using the \hgopt{qinit}{-c} option to \hgcmd{qinit}, this
1178 will be done for you automatically.
1179 \subsection{The \sfilename{status} file}
1181 The \sfilename{status} file contains the names and changeset hashes of
1182 all patches that MQ currently has applied. Unlike the
1183 \sfilename{series} file, this file is not intended for editing. You
1184 should not place this file under revision control, or modify it in any
1185 way. It is used by MQ strictly for internal book-keeping.
1187 %%% Local Variables:
1188 %%% mode: latex
1189 %%% TeX-master: "00book"
1190 %%% End: