2 A tour of git: the basics
6 This document is a modified version originally known as "Distributed
7 revision control with Mercurial" and originally authored by Bryan
8 O’Sullivan. The original document was obtained from
9 <http://hgbook.red-bean.com/>.
11 Copyright © 2006, 2007 Bryan O’Sullivan.
13 This material may be distributed only subject to the terms and
14 conditions set forth in version 1.0 of the Open Publication
15 License. Please refer to Appendix D for the license text.
17 As this is a modified version, the name of Bryan O'Sullivan is used
18 only to properly credit him with the original text. The appearance of
19 his name here explicitly does not assert or imply his endorsement of
20 this modified document.
22 Portions Copyright © 2007 Carl Worth.
24 Changes made by Carl include the following:
27 * Convert from HTML to markdown source syntax
28 * Eliminate all content except Chapter 2 and Appendix D
29 * Eliminate line numbers from examples
30 * Modified to describe git instead of mercurial
32 ### 2.1 Installing git on your system
34 Prebuilt binary packages of git are available for many popular
35 operating systems. These make it easy to start using git on your
40 Because each Linux distribution has its own packaging tools, policies,
41 and rate of development, it’s difficult to give a comprehensive set of
42 instructions on how to install git binaries. The version of
43 git that you will end up with can vary depending on how active
44 the person is who maintains the package for your distribution.
46 To keep things simple, I will focus on installing git from the
47 command line under the most popular Linux distributions. Most of these
48 distributions provide graphical package managers that will let you
49 install git with a single click. The package name to look for is
50 often git, but is sometimes git-core, (due to an unfortunate name
51 with git, meaning GNU Interactive Tools).
55 apt-get install git-core
75 A git-core package is available through
76 [macports](http://macports.org). Once macports is enabled, the command
83 Git has long been available as part of cygwin, and works reasonably
84 well in that environment. Some people find cygwin a particularly
85 inelegant approach to running git and would prefer a "native"
86 solution. To this end, the [msysgit
87 project](http://code.google.com/p/msysgit/) is rapidly putting
88 together a solution including various packages with full
89 installers. These include GitMe, a package to install the entire
90 development environment necessary to work on improving the msysgit
91 port of git, and WinGit, a package for installing just git itself
92 without the development environment, (still in Alpha as of September
95 ### 2.2 Getting started
97 To begin, we’ll use the “git version” command to find out whether git
98 is actually installed properly. Versions 1.5 and newer of git are much
99 more friendly to new users than versions 1.4 and older. If you aren't
100 yet running version 1.5 or newer, it's highly recommended that you
106 #### 2.2.1 Built-in help
108 Git provides a built-in help system. This is invaluable for those
109 times when you find yourself stuck trying to remember how to run a
110 command. If you are completely stuck, simply run “git help”; it will
111 print a brief list of commonly-used commands, along with a description
112 of what each does. If you ask for help on a specific command (such as
113 "git help init"), it prints more detailed information. [XXX: Does "git
114 help <foo>" work universally as a built-in or does it expect man to be
115 present and just call out to "man git-<foo>"?]
117 [XXX: The original hgbook includes the complete output of "hg
118 help init" at this point. I'm not including the corresponding
119 "git help init" output as it would be excessively long. The
120 description alone is quite reasonable, (other than a
121 not-too-helpful aside about the obsolete git-init-db command),
122 but it only comes after a full screen's worth of options
123 details. Might it make sense to have a more summarized help
124 output for "git help <foo>" than all of the documentation
125 available for git-<foo>? And perhaps alos provide a "git -v
126 help" similar to "hg -v help" for more?]
128 ### 2.3 Working with a repository
130 In git, everything happens inside a repository. The repository
131 for a project contains all of the files that “belong to” that project,
132 along with a historical record of the project’s files.
134 There’s nothing particularly magical about a repository; it is simply
135 a directory tree in your filesystem that git treats as
136 special. You can rename or delete a repository any time you like,
137 using either the command line or your file browser.
139 #### 2.3.1 Making a local copy of a repository
141 Copying a repository is just a little bit special. While you could use
142 a normal file copying command to make a copy of a repository, it’s
143 best to use a built-in command that git provides. This command
144 is called “git clone”, because it creates an identical copy of an
147 $ git clone git://cworth.org/git/hello
148 Initialized empty Git repository in /tmp/hello/.git/
149 remote: Generating pack...
150 remote: Done counting 15 objects.
151 remote: Deltifying 15 objects...
152 remote: 100% (15/15) done
153 remote: Total 15 (delta 2), reused 0 (delta 0)
154 Indexing 15 objects...
156 Resolving 2 deltas...
159 If for some reason you are prevented from talking on the git: port,
160 then there is also the capability to clone a repository (less
161 efficiently) over http:
163 $ git clone http://cworth.org/git/hello
164 Initialized empty Git repository in /tmp/hello/.git/
165 got 8e5536eaf0c9313cfcfd3bb915c7ebb63d6f7a91
166 walk 8e5536eaf0c9313cfcfd3bb915c7ebb63d6f7a91
167 got e4c1447f272c0f90e0a80e55f495ec377863f6f5
168 got d884386a016f03bdd6c2c72ceba5621568cc0329
169 got 350a36688de4ee9dfeba52f09bf02385cb967bb2
170 walk d884386a016f03bdd6c2c72ceba5621568cc0329
171 got 9a3ff79a7c30a4b990d49fe7c9095d6bd2eab6c0
172 got ab82c5460482579faae7841e8da3b98fbb34a41c
173 got e19aeb100a31497481bba401cea42a39fac230ae
174 walk e19aeb100a31497481bba401cea42a39fac230ae
175 got 80b260cae9cec3cd52d27c46741ff59c321b852c
176 got 23f952d3dccd5524c3c1b48b3558a5b7393286c2
177 got 9fa6a8464b692252de9a3a20c9e579700d613b17
178 walk 9fa6a8464b692252de9a3a20c9e579700d613b17
179 got b8937ca165a312157658a67e7d413dd59e6ad377
180 got b3f85f210ff86d334575f64cb01c5bf49895b63e
181 got 556e69f96b04bff82857ddd7f7c08b2f3231d664
182 walk 556e69f96b04bff82857ddd7f7c08b2f3231d664
183 got ed55ec04ebc1736a91997a6ce7d7091010647c3d
184 got 43d727f2f3f2f7cb3b098ddad1d7038464a4cee2
186 If our clone succeeded, we should now have a local directory called
187 hello. This directory will contain some files.
191 drwxr-xr-x 3 cworth cworth 4096 2007-09-27 16:40 hello
195 These files have the same contents and history in our repository as
196 they do in the repository we cloned.
198 Every git repository is complete, self-contained, and
199 independent. It contains its own private copy of a project’s files and
200 history. A cloned repository remembers the location of the repository
201 it was cloned from, but it does not communicate with that repository,
202 or any other, unless you tell it to.
204 What this means for now is that we’re free to experiment with our
205 repository, safe in the knowledge that it’s a private “sandbox” that
206 won’t affect anyone else.
208 #### 2.3.2 What’s in a repository?
210 When we take a more detailed look inside a repository, we can see that
211 it contains a directory named .git. This is where git keeps all
212 of its metadata for the repository.
216 . .. .git hello.c Makefile
218 The contents of the .git directory and its subdirectories are private
219 to git. Every other file and directory in the repository is
220 yours to do with as you please.
222 To introduce a little terminology, the .git directory is the “real”
223 repository, and all of the files and directories that coexist with it
224 are said to live in the working directory. An easy way to remember the
225 distinction is that the repository contains the history of your
226 project, while the working directory contains a snapshot of your
227 project at a particular point in history.
229 ### 2.4 A tour through history
231 One of the first things we might want to do with a new, unfamiliar
232 repository is understand its history. The “hg log” command gives us a
236 changeset: 4:b57f9a090b62
238 user: Bryan O'Sullivan <bos@serpentine.com>
239 date: Tue Sep 06 15:43:07 2005 -0700
240 summary: Trim comments.
242 changeset: 3:ff5d7b70a2a9
243 user: Bryan O'Sullivan <bos@serpentine.com>
244 date: Tue Sep 06 13:15:58 2005 -0700
245 summary: Get make to generate the final binary from a .o file.
247 changeset: 2:057d3c2d823c
248 user: Bryan O'Sullivan <bos@serpentine.com>
249 date: Tue Sep 06 13:15:43 2005 -0700
250 summary: Introduce a typo into hello.c.
252 changeset: 1:82e55d328c8c
253 user: mpm@selenic.com
254 date: Fri Aug 26 01:21:28 2005 -0700
255 summary: Create a makefile
257 changeset: 0:0a04b987be5a
258 user: mpm@selenic.com
259 date: Fri Aug 26 01:20:50 2005 -0700
260 summary: Create a standard "hello, world" program
263 By default, this command prints a brief paragraph of output for each
264 change to the project that was recorded. In git terminology, we
265 call each of these recorded events a changeset, because it can contain
266 a record of changes to several files.
268 The fields in a record of output from “hg log” are as follows.
270 * changeset This field has the format of a number, followed by a
271 colon, followed by a hexadecimal string. These are identifiers for
272 the changeset. There are two identifiers because the number is
273 shorter and easier to type than the hex string.
274 * user The identity of the person who created the changeset. This is
275 a free-form field, but it most often contains a person’s name and
277 * date The date and time on which the changeset was created, and the
278 timezone in which it was created. (The date and time are local to
279 that timezone; they display what time and date it was for the
280 person who created the changeset.)
281 * summary The first line of the text message that the creator of the
282 changeset entered to describe the changeset.
284 The default output printed by “hg log” is purely a summary; it is
285 missing a lot of detail.
287 Figure [2.1][8] provides a graphical representation of the history of
288 the hello repository, to make it a little easier to see which
289 direction history is “flowing” in. We’ll be returning to this figure
290 several times in this chapter and the chapter that follows.
297 Graphical history of the hello repository
301 #### 2.4.1 Changesets, revisions, and talking to other people
303 As English is a notoriously sloppy language, and computer science has
304 a hallowed history of terminological confusion (why use one term when
305 four will do?), revision control has a variety of words and phrases
306 that mean the same thing. If you are talking about Mercurial history
307 with other people, you will find that the word “changeset” is often
308 compressed to “change” or (when written) “cset”, and sometimes a
309 changeset is referred to as a “revision” or a “rev”.
311 While it doesn’t matter what word you use to refer to the concept of
312 “a changeset”, the identifier that you use to refer to “a specific
313 changeset” is of great importance. Recall that the changeset field in
314 the output from “hg log” identifies a changeset using both a number
315 and a hexadecimal string.
317 * The revision number is only valid in that repository,
318 * while the hex string is the permanent, unchanging identifier that
319 will always identify that exact changeset in every copy of the
322 This distinction is important. If you send someone an email talking
323 about “revision 33”, there’s a high likelihood that their revision 33
324 will not be the same as yours. The reason for this is that a revision
325 number depends on the order in which changes arrived in a repository,
326 and there is no guarantee that the same changes will happen in the
327 same order in different repositories. Three changes a,b,c can easily
328 appear in one repository as 0,1,2, while in another as 1,0,2.
330 Mercurial uses revision numbers purely as a convenient shorthand. If
331 you need to discuss a changeset with someone, or make a record of a
332 changeset for some other reason (for example, in a bug report), use
333 the hexadecimal identifier.
335 #### 2.4.2 Viewing specific revisions
337 To narrow the output of “hg log” down to a single revision, use the -r
338 (or --rev) option. You can use either a revision number or a long-form
339 changeset identifier, and you can provide as many revisions as you
343 changeset: 3:ff5d7b70a2a9
344 user: Bryan O'Sullivan <bos@serpentine.com>
345 date: Tue Sep 06 13:15:58 2005 -0700
346 summary: Get make to generate the final binary from a .o file.
348 $ hg log -r ff5d7b70a2a9
349 changeset: 3:ff5d7b70a2a9
350 user: Bryan O'Sullivan <bos@serpentine.com>
351 date: Tue Sep 06 13:15:58 2005 -0700
352 summary: Get make to generate the final binary from a .o file.
355 changeset: 1:82e55d328c8c
356 user: mpm@selenic.com
357 date: Fri Aug 26 01:21:28 2005 -0700
358 summary: Create a makefile
360 changeset: 4:b57f9a090b62
362 user: Bryan O'Sullivan <bos@serpentine.com>
363 date: Tue Sep 06 15:43:07 2005 -0700
364 summary: Trim comments.
367 If you want to see the history of several revisions without having to
368 list each one, you can use range notation; this lets you express the
369 idea “I want all revisions between a and b, inclusive”.
372 changeset: 2:057d3c2d823c
373 user: Bryan O'Sullivan <bos@serpentine.com>
374 date: Tue Sep 06 13:15:43 2005 -0700
375 summary: Introduce a typo into hello.c.
377 changeset: 3:ff5d7b70a2a9
378 user: Bryan O'Sullivan <bos@serpentine.com>
379 date: Tue Sep 06 13:15:58 2005 -0700
380 summary: Get make to generate the final binary from a .o file.
382 changeset: 4:b57f9a090b62
384 user: Bryan O'Sullivan <bos@serpentine.com>
385 date: Tue Sep 06 15:43:07 2005 -0700
386 summary: Trim comments.
389 Mercurial also honours the order in which you specify revisions, so
390 “hg log -r 2:4” prints 2,3,4 while “hg log -r 4:2” prints 4,3,2.
392 #### 2.4.3 More detailed information
394 While the summary information printed by “hg log” is useful if you
395 already know what you’re looking for, you may need to see a complete
396 description of the change, or a list of the files changed, if you’re
397 trying to decide whether a changeset is the one you’re looking
398 for. The “hg log” command’s -v (or --verbose) option gives you this
402 changeset: 3:ff5d7b70a2a9
403 user: Bryan O'Sullivan <bos@serpentine.com>
404 date: Tue Sep 06 13:15:58 2005 -0700
407 Get make to generate the final binary from a .o file.
411 If you want to see both the description and content of a change, add
412 the -p (or --patch) option. This displays the content of a change as a
413 unified diff (if you’ve never seen a unified diff before, see
414 section [12.4][10] for an overview).
417 changeset: 2:057d3c2d823c
418 user: Bryan O'Sullivan <bos@serpentine.com>
419 date: Tue Sep 06 13:15:43 2005 -0700
422 Introduce a typo into hello.c.
425 diff -r 82e55d328c8c -r 057d3c2d823c hello.c
426 --- a/hello.c Fri Aug 26 01:21:28 2005 -0700
427 +++ b/hello.c Tue Sep 06 13:15:43 2005 -0700
430 int main(int argc, char ⋆⋆argv)
432 - printf("hello, world!∖n");
433 + printf("hello, world!∖");
438 ### 2.5 All about command options
440 Let’s take a brief break from exploring Mercurial commands to discuss
441 a pattern in the way that they work; you may find this useful to keep
442 in mind as we continue our tour.
444 Mercurial has a consistent and straightforward approach to dealing
445 with the options that you can pass to commands. It follows the
446 conventions for options that are common to modern Linux and Unix
449 * Every option has a long name. For example, as we’ve already seen,
450 the “hg log” command accepts a --rev option.
451 * Most options have short names, too. Instead of --rev, we can use
452 -r. (The reason that some options don’t have short names is that
453 the options in question are rarely used.)
454 * Long options start with two dashes (e.g. --rev), while short
455 options start with one (e.g. -r).
456 * Option naming and usage is consistent across commands. For
457 example, every command that lets you specify a changeset ID or
458 revision number accepts both -r and --rev arguments.
460 In the examples throughout this book, I use short options instead of
461 long. This just reflects my own preference, so don’t read anything
464 Most commands that print output of some kind will print more output
465 when passed a -v (or --verbose) option, and less when passed -q (or
468 ### 2.6 Making and reviewing changes
470 Now that we have a grasp of viewing history in Mercurial, let’s take a
471 look at making some changes and examining them.
473 The first thing we’ll do is isolate our experiment in a repository of
474 its own. We use the “hg clone” command, but we don’t need to clone a
475 copy of the remote repository. Since we already have a copy of it
476 locally, we can just clone that instead. This is much faster than
477 cloning over the network, and cloning a local repository uses less
478 disk space in most cases, too.
481 $ hg clone hello my-hello
482 2 files updated, 0 files merged, 0 files removed, 0 files unresolved
485 As an aside, it’s often good practice to keep a “pristine” copy of a
486 remote repository around, which you can then make temporary clones of
487 to create sandboxes for each task you want to work on. This lets you
488 work on multiple tasks in parallel, each isolated from the others
489 until it’s complete and you’re ready to integrate it back. Because
490 local clones are so cheap, there’s almost no overhead to cloning and
491 destroying repositories whenever you want.
493 In our my-hello repository, we have a file hello.c that contains the
494 classic “hello, world” program. Let’s use the ancient and venerable
495 sed command to edit this file so that it prints a second line of
496 output. (I’m only using sed to do this because it’s easy to write a
497 scripted example this way. Since you’re not under the same constraint,
498 you probably won’t want to use sed; simply use your preferred text
499 editor to do the same thing.)
501 $ sed -i '/printf/a∖∖tprintf("hello again!∖∖n");' hello.c
503 Mercurial’s “hg status” command will tell us what Mercurial knows
504 about the files in the repository.
511 The “hg status” command prints no output for some files, but a line
512 starting with “M” for hello.c. Unless you tell it to, “hg status” will
513 not print any output for files that have not been modified.
515 The “M” indicates that Mercurial has noticed that we modified
516 hello.c. We didn’t need to inform Mercurial that we were going to
517 modify the file before we started, or that we had modified the file
518 after we were done; it was able to figure this out itself.
520 It’s a little bit helpful to know that we’ve modified hello.c, but we
521 might prefer to know exactly what changes we’ve made to it. To do
522 this, we use the “hg diff” command.
525 diff -r b57f9a090b62 hello.c
526 --- a/hello.c Tue Sep 06 15:43:07 2005 -0700
527 +++ b/hello.c Sun Jun 17 18:05:50 2007 +0000
528 @@ -8,5 +8,6 @@ int main(int argc, char ⋆⋆argv)
529 int main(int argc, char ⋆⋆argv)
531 printf("hello, world!∖");
532 + printf("hello again!∖n");
536 ### 2.7 Recording changes in a new changeset
538 We can modify files, build and test our changes, and use “hg status”
539 and “hg diff” to review our changes, until we’re satisfied with what
540 we’ve done and arrive at a natural stopping point where we want to
541 record our work in a new changeset.
543 The “hg commit” command lets us create a new changeset; we’ll usually
544 refer to this as “making a commit” or “committing”.
546 #### 2.7.1 Setting up a username
548 When you try to run “hg commit” for the first time, it is not
549 guaranteed to succeed. Mercurial records your name and address with
550 each change that you commit, so that you and others will later be able
551 to tell who made each change. Mercurial tries to automatically figure
552 out a sensible username to commit the change with. It will attempt
553 each of the following methods, in order:
555 1. If you specify a -u option to the “hg commit” command on the
556 command line, followed by a username, this is always given the
558 2. If you have set the HGUSER environment variable, this is checked next.
559 3. If you create a file in your home directory called .hgrc, with a
560 username entry, that will be used next. To see what the contents
561 of this file should look like, refer to section [2.7.1][11]
563 4. If you have set the EMAIL environment variable, this will be used
565 5. Mercurial will query your system to find out your local user name
566 and host name, and construct a username from these
567 components. Since this often results in a username that is not
568 very useful, it will print a warning if it has to do this.
570 If all of these mechanisms fail, Mercurial will fail, printing an
571 error message. In this case, it will not let you commit until you set
574 You should think of the HGUSER environment variable and the -u option
575 to the “hg commit” command as ways to override Mercurial’s default
576 selection of username. For normal use, the simplest and most robust
577 way to set a username for yourself is by creating a .hgrc file; see
580 ##### Creating a Mercurial configuration file
582 To set a user name, use your favourite editor to create a file called
583 .hgrc in your home directory. Mercurial will use this file to look up
584 your personalised configuration settings. The initial contents of your
585 .hgrc should look like this.
587 # This is a Mercurial configuration file.
589 username = Firstname Lastname <email.address@domain.net>
591 The “[ui]” line begins a section of the config file, so you can read
592 the “username = ...” line as meaning “set the value of the username
593 item in the ui section”. A section continues until a new section
594 begins, or the end of the file. Mercurial ignores empty lines and
595 treats any text from “#” to the end of a line as a comment.
597 ##### Choosing a user name
599 You can use any text you like as the value of the username config
600 item, since this information is for reading by other people, but for
601 interpreting by Mercurial. The convention that most people follow is
602 to use their name and email address, as in the example above.
604 Note: Mercurial’s built-in web server obfuscates email addresses, to
605 make it more difficult for the email harvesting tools that spammers
606 use. This reduces the likelihood that you’ll start receiving more junk
607 email if you publish a Mercurial repository on the web.
609 #### 2.7.2 Writing a commit message
611 When we commit a change, Mercurial drops us into a text editor, to
612 enter a message that will describe the modifications we’ve made in
613 this changeset. This is called the commit message. It will be a record
614 for readers of what we did and why, and it will be printed by “hg log”
615 after we’ve finished committing.
619 The editor that the “hg commit” command drops us into will contain an
620 empty line, followed by a number of lines starting with “HG:”.
625 Mercurial ignores the lines that start with “HG:”; it uses them only
626 to tell us which files it’s recording changes to. Modifying or
627 deleting these lines has no effect.
629 #### 2.7.3 Writing a good commit message
631 Since “hg log” only prints the first line of a commit message by
632 default, it’s best to write a commit message whose first line stands
633 alone. Here’s a real example of a commit message that doesn’t follow
634 this guideline, and hence has a summary that is not readable.
636 changeset: 73:584af0e231be
637 user: Censored Person <censored.person@example.org>
638 date: Tue Sep 26 21:37:07 2006 -0700
639 summary: include buildmeister/commondefs. Add an exports and install
641 As far as the remainder of the contents of the commit message are
642 concerned, there are no hard-and-fast rules. Mercurial itself doesn’t
643 interpret or care about the contents of the commit message, though
644 your project may have policies that dictate a certain kind of
647 My personal preference is for short, but informative, commit messages
648 that tell me something that I can’t figure out with a quick glance at
649 the output of “hg log --patch”.
651 #### 2.7.4 Aborting a commit
653 If you decide that you don’t want to commit while in the middle of
654 editing a commit message, simply exit from your editor without saving
655 the file that it’s editing. This will cause nothing to happen to
656 either the repository or the working directory.
658 If we run the “hg commit” command without any arguments, it records
659 all of the changes we’ve made, as reported by “hg status” and “hg
662 #### 2.7.5 Admiring our new handiwork
664 Once we’ve finished the commit, we can use the “hg tip” command to
665 display the changeset we just created. This command produces output
666 that is identical to “hg log”, but it only displays the newest
667 revision in the repository.
670 changeset: 5:fa1321bf0c80
672 user: Bryan O'Sullivan <bos@serpentine.com>
673 date: Sun Jun 17 18:05:50 2007 +0000
676 Added an extra line of output
679 diff -r b57f9a090b62 -r fa1321bf0c80 hello.c
680 --- a/hello.c Tue Sep 06 15:43:07 2005 -0700
681 +++ b/hello.c Sun Jun 17 18:05:50 2007 +0000
682 @@ -8,5 +8,6 @@ int main(int argc, char ⋆⋆argv)
683 int main(int argc, char ⋆⋆argv)
685 printf("hello, world!∖");
686 + printf("hello again!∖n");
691 We refer to the newest revision in the repository as the tip revision,
694 ### 2.8 Sharing changes
696 We mentioned earlier that repositories in Mercurial are
697 self-contained. This means that the changeset we just created exists
698 only in our my-hello repository. Let’s look at a few ways that we can
699 propagate this change into other repositories.
701 #### 2.8.1 Pulling changes from another repository
703 To get started, let’s clone our original hello repository, which does
704 not contain the change we just committed. We’ll call our temporary
705 repository hello-pull.
708 $ hg clone hello hello-pull
709 2 files updated, 0 files merged, 0 files removed, 0 files unresolved
711 We’ll use the “hg pull” command to bring changes from my-hello into
712 hello-pull. However, blindly pulling unknown changes into a repository
713 is a somewhat scary prospect. Mercurial provides the “hg incoming”
714 command to tell us what changes the “hg pull” command would pull into
715 the repository, without actually pulling the changes in.
718 $ hg incoming ../my-hello
719 comparing with ../my-hello
720 searching for changes
721 changeset: 5:fa1321bf0c80
723 user: Bryan O'Sullivan <bos@serpentine.com>
724 date: Sun Jun 17 18:05:50 2007 +0000
725 summary: Added an extra line of output
728 (Of course, someone could cause more changesets to appear in the
729 repository that we ran “hg incoming” in, before we get a chance to “hg
730 pull” the changes, so that we could end up pulling changes that we
733 Bringing changes into a repository is a simple matter of running the
734 “hg pull” command, and telling it which repository to pull from.
737 changeset: 4:b57f9a090b62
739 user: Bryan O'Sullivan <bos@serpentine.com>
740 date: Tue Sep 06 15:43:07 2005 -0700
741 summary: Trim comments.
743 $ hg pull ../my-hello
744 pulling from ../my-hello
745 searching for changes
749 added 1 changesets with 1 changes to 1 files
750 (run 'hg update' to get a working copy)
752 changeset: 5:fa1321bf0c80
754 user: Bryan O'Sullivan <bos@serpentine.com>
755 date: Sun Jun 17 18:05:50 2007 +0000
756 summary: Added an extra line of output
759 As you can see from the before-and-after output of “hg tip”, we have
760 successfully pulled changes into our repository. There remains one
761 step before we can see these changes in the working directory.
763 #### 2.8.2 Updating the working directory
765 We have so far glossed over the relationship between a repository and
766 its working directory. The “hg pull” command that we ran in
767 section [2.8.1][12] brought changes into the repository, but if we
768 check, there’s no sign of those changes in the working directory. This
769 is because “hg pull” does not (by default) touch the working
770 directory. Instead, we use the “hg update” command to do this.
772 $ grep printf hello.c
773 printf("hello, world!∖");
775 1 files updated, 0 files merged, 0 files removed, 0 files unresolved
776 $ grep printf hello.c
777 printf("hello, world!∖");
778 printf("hello again!∖n");
780 It might seem a bit strange that “hg pull” doesn’t update the working
781 directory automatically. There’s actually a good reason for this: you
782 can use “hg update” to update the working directory to the state it
783 was in at any revision in the history of the repository. If you had
784 the working directory updated to an old revision—to hunt down the
785 origin of a bug, say—and ran a “hg pull” which automatically updated
786 the working directory to a new revision, you might not be terribly
789 However, since pull-then-update is such a common thing to do,
790 Mercurial lets you combine the two by passing the -u option to “hg
795 If you look back at the output of “hg pull” in section [2.8.1][12]
796 when we ran it without -u, you can see that it printed a helpful
797 reminder that we’d have to take an explicit step to update the working
800 (run 'hg update' to get a working copy)
802 To find out what revision the working directory is at, use the “hg
806 changeset: 5:fa1321bf0c80
808 user: Bryan O'Sullivan <bos@serpentine.com>
809 date: Sun Jun 17 18:05:50 2007 +0000
810 summary: Added an extra line of output
813 If you look back at figure [2.1][8], you’ll see arrows connecting each
814 changeset. The node that the arrow leads from in each case is a
815 parent, and the node that the arrow leads to is its child. The working
816 directory has a parent in just the same way; this is the changeset
817 that the working directory currently contains.
819 To update the working directory to a particular revision, give a
820 revision number or changeset ID to the “hg update” command.
823 2 files updated, 0 files merged, 0 files removed, 0 files unresolved
825 changeset: 2:057d3c2d823c
826 user: Bryan O'Sullivan <bos@serpentine.com>
827 date: Tue Sep 06 13:15:43 2005 -0700
828 summary: Introduce a typo into hello.c.
831 2 files updated, 0 files merged, 0 files removed, 0 files unresolved
833 If you omit an explicit revision, “hg update” will update to the tip
834 revision, as shown by the second call to “hg update” in the example
837 #### 2.8.3 Pushing changes to another repository
839 Mercurial lets us push changes to another repository, from the
840 repository we’re currently visiting. As with the example of “hg pull”
841 above, we’ll create a temporary repository to push our changes into.
844 $ hg clone hello hello-push
845 2 files updated, 0 files merged, 0 files removed, 0 files unresolved
847 The “hg outgoing” command tells us what changes would be pushed into
851 $ hg outgoing ../hello-push
852 comparing with ../hello-push
853 searching for changes
854 changeset: 5:fa1321bf0c80
856 user: Bryan O'Sullivan <bos@serpentine.com>
857 date: Sun Jun 17 18:05:50 2007 +0000
858 summary: Added an extra line of output
861 And the “hg push” command does the actual push.
863 $ hg push ../hello-push
864 pushing to ../hello-push
865 searching for changes
869 added 1 changesets with 1 changes to 1 files
871 As with “hg pull”, the “hg push” command does not update the working
872 directory in the repository that it’s pushing changes into. (Unlike
873 “hg pull”, “hg push” does not provide a -u option that updates the
874 other repository’s working directory.)
876 What happens if we try to pull or push changes and the receiving
877 repository already has those changes? Nothing too exciting.
879 $ hg push ../hello-push
880 pushing to ../hello-push
881 searching for changes
884 #### 2.8.4 Sharing changes over a network
886 The commands we have covered in the previous few sections are not
887 limited to working with local repositories. Each works in exactly the
888 same fashion over a network connection; simply pass in a URL instead
891 $ hg outgoing http://hg.serpentine.com/tutorial/hello
892 comparing with http://hg.serpentine.com/tutorial/hello
893 searching for changes
894 changeset: 5:fa1321bf0c80
896 user: Bryan O'Sullivan <bos@serpentine.com>
897 date: Sun Jun 17 18:05:50 2007 +0000
898 summary: Added an extra line of output
901 In this example, we can see what changes we could push to the remote
902 repository, but the repository is understandably not set up to let
903 anonymous users push to it.
905 $ hg push http://hg.serpentine.com/tutorial/hello
906 pushing to http://hg.serpentine.com/tutorial/hello
907 searching for changes
910 [1]: http://hgbook.red-bean.com/hgbookch3.html
911 [2]: http://hgbook.red-bean.com/hgbookch1.html
912 [3]: http://hgbook.red-bean.com/hgbookch1.html#tailhgbookch1.html
913 [4]: #tailhgbookch2.html
914 [5]: http://hgbook.red-bean.com/hgbook.html#hgbookch2.html
915 [6]: http://mercurial.berkwood.com/
916 [7]: http://hgbook.red-bean.com/hgbookli4.html#Xweb:macpython
918 [9]: hgbookch2_files/tour-history.png
919 [10]: http://hgbook.red-bean.com/hgbookch12.html#x16-27100012.4
922 [13]: http://hgbook.red-bean.com/hgbookch2.html
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