2 Title: Collecting information about git
5 Author: Oleg Broytman <phd@phdru.name>
8 Content-Type: text/x-rst
15 This Informational PEP collects information about git. There is, of
16 course, a lot of documentation for git, so the PEP concentrates on
17 more complex issues, scenarios and topics.
19 The plan is to extend the PEP in the future collecting information
20 about equivalence of Mercurial and git scenarios to help migrating
21 Python development from Mercurial to git.
23 The author of the PEP doesn't currently plan to write a Process PEP on
24 migration from Mercurial to git.
30 Git is accompanied with a lot of documentation, both online and
33 Documentation for starters
34 --------------------------
37 <https://www.kernel.org/pub/software/scm/git/docs/gittutorial.html>`_,
39 <https://www.kernel.org/pub/software/scm/git/docs/gittutorial-2.html>`_.
42 <https://www.kernel.org/pub/software/scm/git/docs/user-manual.html>`_.
43 `Everyday GIT With 20 Commands Or So
44 <https://www.kernel.org/pub/software/scm/git/docs/everyday.html>`_.
46 <https://www.kernel.org/pub/software/scm/git/docs/gitworkflows.html>`_.
49 <http://www-cs-students.stanford.edu/~blynn/gitmagic/index.html>`_,
50 also with a number of translations.
52 Advanced documentation
53 ----------------------
55 `Pro Git <https://git-scm.com/book>`_. The Book about git. Buy it at
56 Amazon or download in PDF, mobi, or ePub form. Has translations to
57 many different languages. Download Russian translation from `GArik
58 <https://github.com/GArik/progit/wiki>`_.
60 `Git Wiki <https://git.wiki.kernel.org/index.php/Main_Page>`_.
65 Git has builtin help: run ``git help TOPIC``. For example, run
66 ``git help git`` or ``git help help``.
72 Download and installation
73 -------------------------
75 Unix users: download and install using your package manager.
77 Microsoft Windows: download `git-for-windows
78 <https://github.com/git-for-windows/git/releases>`_ or `msysGit
79 <https://github.com/msysgit/msysgit/releases>`_.
81 MacOS X: use git installed with `XCode
82 <https://developer.apple.com/xcode/downloads/>`_ or download
84 <http://sourceforge.net/projects/git-osx-installer/files/>`_.
89 This simple code is often appears in documentation, but it is
90 important so let repeat it here. Git marks every commit with author
91 and committer names/emails, so configure your real name and preferred
94 $ git config --global user.name "User Name"
95 $ git config --global user.email user.name@example.org
101 Examples of git commands in this PEP use the following approach. It is
102 supposed that you, the user, works with a local repository named
103 ``python`` that has an upstream remote repo named ``origin``. Your
104 local repo has two branches ``v1`` and ``v2``. For most examples the
105 currently checked out branch is ``v2``. That is, it's assumed you have
106 done something like that::
108 $ git clone -b v2 http://git.python.org/python.git
110 $ git branch v1 origin/v1
112 The last command creates a new local branch v1 and sets
113 remotes/origin/v1 as its upstream remote branch.
115 The same result can achieved with commands::
117 $ git clone -b v1 http://git.python.org/python.git
119 $ git checkout --track origin/v2
121 The last command creates a new local branch v2, sets
122 remotes/origin/v2 as its upstream remote branch and checks it out into
123 the working directory.
126 Branches and branches
127 =====================
129 Git terminology can be a bit misleading. Take, for example, the term
130 "branch". In git it has two meanings. A branch is a directed line of
131 commits (possibly with merges). And a branch is a label or a pointer
132 assigned to a line of commits. It is important to differentiate when
133 you talk about commits and when about their labels. Lines of commits
134 are by itself unnamed and are usually only lengthening and merging.
135 Labels, on the other hand, can be created, moved, renamed and deleted
139 Remote repository and remote branches
140 =====================================
142 Another example of slightly misleading terminology. Remote
143 repositories are really remote, you access them via network (well, a
144 remote repository can be on your local disk, but it's still remote
145 because it's not the current repo).
147 Remote branches, on the other hand, are branches (pointers to commits)
148 in your local repository. They are there for you to remember what
149 branches and commits have been pulled from and pushed to what remote
150 repos (you can pull from and push to many remotes). Remote branches
151 live under ``remotes/REMOTE`` namespaces, e.g. ``remotes/origin/v2``.
153 To see the status of remote branches run::
157 To see local and remote branches (and tags) pointing to commits::
161 You never do your own development on remote branches. You create a
162 local branch that has a remote branch as upstream and do development
163 on that local branch. On push git updates remote branches, and on pull
164 git updates remote branches and fast-forwards, merges or rebases local
167 When you do an initial clone like this::
169 $ git clone -b v1 http://git.python.org/python.git
171 git clones remote repository ``http://git.python.org/python.git`` to
172 directory ``python``, creates remote branches and checks out branch
173 ``v1`` into the working directory.
175 Updating local and remote branches
176 ----------------------------------
178 There is a major difference between
182 $ git fetch REMOTE BRANCH
188 $ git fetch REMOTE BRANCH:BRANCH
190 The first command fetches commits from the named BRANCH in the REMOTE
191 repository that are not in your repository and leaves the id (the
192 hash) of the head commit in file .git/FETCH_HEAD. But it doesn't
193 update any branch (doesn't move any pointer).
195 The second command fetches commits from the named BRANCH in the REMOTE
196 repository that are not in your repository and updates both the local
197 branch BRANCH and its upstream remote branch. But it refuses to update
198 branches in case of non-fast-forward. And it refuses to update the
201 The first command is used internally by ``git pull``.
205 $ git pull REMOTE BRANCH
211 $ git fetch REMOTE BRANCH
212 $ git merge FETCH_HEAD # FETCH_HEAD is a literal here
214 Certainly, BRANCH in that case should be your current branch. If you
215 want to merge a different branch into your current branch first update
216 that non-current branch and then merge::
218 $ git fetch origin v1:v1 # Update v1
219 $ git pull --rebase origin v2 # Update the current branch v2 using
220 # rebase instead of merge
223 It is possible to configure git to make it fetch/pull a few branches
224 or all branches at once, so you can simply run
239 Pushing is a bit simpler. There is only one command ``push``. When you
244 $ git push origin v1 v2
246 git guesses (knowing upstream remote branches) that you really want
250 $ git push origin v1:v1 v2:v2
252 Git pushes commits to the remote repo and updates remote branches. Git
253 refuses to push commits that aren't fast-forwardable. You can
254 force-push anyway, but please remember - you can force-push to your
255 own repositories but don't force-push to public or shared repos. If
256 you find git refuses to push commits that aren't fast-forwardable,
257 better fetch and merge commits from the remote repo (or rebase your
258 commits on top of the fetched commits), then push. Only force-push if
259 you know what you do and why you do it. See the section `Commit
260 editing and caveats`_ below.
262 It is possible to configure git to make it push a few branches or all
263 branches at once, so you can simply run
275 Git refuses to push a branch if it's the current branch in the remote
276 non-bare repository: git refuses to update remote working directory.
277 You really should push only to bare repositories. For non-bare
278 repositories git prefers pull-based workflow.
283 Git automatically fetches tags that point to commits being fetched
284 during fetch/pull. To fetch all tags (and commits they point to) run
285 ``git fetch --tags origin``. To fetch some specific tags fetch them
288 $ git fetch origin tag NAME1 tag NAME2...
292 $ git fetch origin tag 1.4.2 tag 2.1.7
294 Git doesn't automatically pushes tags. That allows you to have private
295 tags (lightweight tags are also private for a repo, they cannot be
296 pushed). To push tag(s) list them explicitly::
298 $ git push origin tag 1.4.2
299 $ git push origin v1 v2 tag 2.1.7
302 Commit editing and caveats
303 ==========================
305 A warning not to edit published (pushed) commits also appears in
306 documentation but it's repeated here anyway as it's very important.
308 It is possible to recover from forced push but it's PITA for the
309 entire team. Please avoid it.
311 To see what commits have not been published yet compare the head of the
312 branch with its upstream remote branch::
314 $ git log origin/v2..
315 $ git log origin/v1..v1
317 For every branch that has an upstream remote branch git maintains an
318 alias @{upstream} (short version @{u}), so the commands above can be
324 To see the status of all branches::
328 To compare the status of local branches with a remote repo::
330 $ git remote show origin
332 Read `how to recover from upstream rebase
333 <https://git-scm.com/docs/git-rebase#_recovering_from_upstream_rebase>`_.
334 It is in ``git help rebase``.
336 On the other hand don't be too afraid about commit editing. You can
337 safely edit, remove, reorder, combine and split commits that hasn't
338 been pushed yet. You can even push commits to your own (backup) repo,
339 edit them later and force-push edited commits to replace what has
340 already been pushed. Not a problem until commits are in a public
341 or shared repository.
347 TODO: describe undo strategies: git reset, git revert, git checkout,
348 git reflog. "Commit early, commit often".
351 https://kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html
360 Staging area aka index is a distinguishing feature of git. See
362 <https://git.wiki.kernel.org/index.php/WhatIsTheIndex>`_ and
363 `IndexCommandQuickref
364 <https://git.wiki.kernel.org/index.php/IndexCommandQuickref>`_ in Git
375 Git has a builtin strategy for what Python core developers call
378 $ git merge -s ours v1 # null-merge v1 into v2
384 https://git-scm.com/book/en/Git-Tools-Rerere
387 Advanced configuration
388 ======================
393 Git has builtin mechanisms to handle line endings.
395 TODO: describe crlf configuration and .gitattributes.
401 TODO: dangling objects, git gc, git repack.
407 TODO: bash/zsh completion, bash/zsh prompt.
410 From Mercurial to git
411 =====================
413 Mercurial for Git users https://mercurial.selenic.com/wiki/GitConcepts
415 https://github.com/felipec/git-remote-hg
417 https://hg-git.github.io/
429 This document has been placed in the public domain.
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