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://git-for-windows.github.io/>`_.
80 MacOS X: use git installed with `XCode
81 <https://developer.apple.com/xcode/downloads/>`_ or download
83 <http://sourceforge.net/projects/git-osx-installer/files/>`_.
88 This simple code is often appears in documentation, but it is
89 important so let repeat it here. Git marks every commit with author
90 and committer names/emails, so configure your real name and preferred
93 $ git config --global user.name "User Name"
94 $ git config --global user.email user.name@example.org
100 Examples of git commands in this PEP use the following approach. It is
101 supposed that you, the user, works with a local repository named
102 ``python`` that has an upstream remote repo named ``origin``. Your
103 local repo has two branches ``v1`` and ``v2``. For most examples the
104 currently checked out branch is ``v2``. That is, it's assumed you did
105 something like that::
107 $ git clone -b v1 http://git.python.org/python.git
109 $ git fetch origin v2:v2
113 Branches and branches
114 =====================
116 Git terminology can be a bit misleading. Take, for example, the term
117 "branch". In git it has two meanings. A branch is a directed line of
118 commits (possibly with merges). And a branch is a label or a pointer
119 assigned to a line of commits. It is important to differentiate when
120 you talk about commits and when about their labels. Lines of commits
121 are by itself unnamed and are usually only lengthening and merging.
122 Labels, on the other hand, can be created, moved, renamed and deleted
126 Remote repository and remote branches
127 =====================================
129 Another example of slightly misleading terminology. Remote
130 repositories are really remote, you access them via network (well, a
131 remote repository can be on your local disk, but it's still remote
132 because it's not the current repo).
134 Remote branches, on the other hand, are branches (pointers to commits)
135 in your local repository. They are there for you to remember what
136 branches and commits have been pulled from and pushed to what remote
137 repos (you can pull from and push to many remotes). Remote branches
138 live under ``remotes/REMOTE`` namespaces, e.g. ``remotes/origin/v2``.
140 To see the status of remote branches run::
144 To see local and remote branches (and tags) pointing to commits::
148 You never do your own development on remote branches. You create a
149 local branch that has a remote branch as an upstream and do
150 development on that local branch. On push git updates remote branches,
151 and on pull git updates remote branches and fast-forwards, merges or
152 rebases local branches.
154 When you do an initial clone like this::
156 $ git clone -b v1 http://git.python.org/python.git
158 git clones remote repository ``http://git.python.org/python.git`` to
159 directory ``python``, creates remote branches and checks out branch
160 ``v1`` into the working directory.
162 Updating local and remote branches
163 ----------------------------------
165 There is a major difference between
169 $ git fetch REMOTE BRANCH
175 $ git fetch REMOTE BRANCH:BRANCH
177 The first command fetches commits from the named BRANCH in the REMOTE
178 repository that are not in your repository and leaves the id (the
179 hash) of the head commit in file .git/FETCH_HEAD. But it doesn't
180 update any branch (doesn't move any pointer).
182 The second command fetches commits from the named BRANCH in the REMOTE
183 repository that are not in your repository and updates both the local
184 branch BRANCH and its upstream remote branch. But it refuses to update
185 branches in case of non-fast-forward. And it refuses to update the
188 The first command is used internally by ``git pull``.
192 $ git pull REMOTE BRANCH
198 $ git fetch REMOTE BRANCH
199 $ git merge FETCH_HEAD # FETCH_HEAD is a literal here
201 Certainly, BRANCH in that case should be your current branch. If you
202 want to merge a different branch into your current branch first update
203 that non-current branch and then merge::
205 $ git fetch origin v1:v1 # Update v1
206 $ git pull --rebase origin v2 # Update the current branch v2 using
207 # rebase instead of merge
210 It is possible to configure git to make it fetch/pull a few branches
211 or all branches at once, so you can simply run
226 Pushing is a bit simpler. There is only one command ``push``. When you
231 $ git push origin v1 v2
233 git guesses (knowing upstream remote branches) that you really want
237 $ git push origin v1:v1 v2:v2
239 Git pushes commits to the remote repo and updates remote branches. Git
240 refuses to push commits that aren't fast-forwardable. You can
241 force-push anyway, but please remember - you can force-push to your
242 own repositories but don't force-push to public or shared repos. If
243 you find git refuses to push commits that aren't fast-forwardable,
244 better fetch and merge commits from the remote repo (or rebase your
245 commits on top of the fetched commits), then push. Only force-push if
246 you know what you do and why you do it. See the section `Commit
247 editing and caveats`_ below.
249 It is possible to configure git to make it push a few branches or all
250 branches at once, so you can simply run
262 Git refuses to push a branch if it's the current branch in the remote
263 non-bare repository: git refuses to update remote working directory.
264 You really should push only to bare repositories. For non-bare
265 repositories git prefers pull-based workflow.
270 Git automatically fetches tags that point to commits being fetched
271 during fetch/pull. To fetch all tags (and commits they point to) run
272 ``git fetch --tags origin``. To fetch some specific tags fetch them
275 $ git fetch origin tag NAME1 tag NAME2...
279 $ git fetch origin tag 1.4.2 tag 2.1.7
281 Git doesn't automatically pushes tags. That allows you to have private
282 tags (lightweight tags are also private for a repo, they cannot be
283 pushed). To push tag(s) list them explicitly::
285 $ git push origin tag 1.4.2
286 $ git push origin v1 v2 tag 2.1.7
289 Commit editing and caveats
290 ==========================
292 A warning not to edit published (pushed) commits also appears in
293 documentation but it's repeated here anyway as it's very important.
295 It is possible to recover from forced push but it's PITA for the
296 entire team. Please avoid it.
298 To see what commits have not been published yet compare the head of the
299 branch with its upstream remote branch::
301 $ git log origin/v2..
302 $ git log origin/v1..v1
304 For every branch that has an upstream remote branch git maintains an
305 alias @{upstream} (short version @{u}), so the commands above can be
311 To see the status of all branches::
315 To compare the status of local branches with a remote repo::
317 $ git remote show origin
319 Read `how to recover from upstream rebase
320 <https://git-scm.com/docs/git-rebase#_recovering_from_upstream_rebase>`_.
321 It is in ``git help rebase``.
323 On the other hand don't be too afraid about commit editing. You can
324 safely edit, remove, reorder, combine and split commits that hasn't
325 been pushed yet. You can even push commits to your own (backup) repo,
326 edit them later and force-push edited commits to replace what has
327 already been pushed. Not a problem until commits are in a public
334 TODO: describe undo strategies: git reset, git revert, git checkout,
335 git reflog. "Commit early, commit often".
338 https://kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html
347 Staging area aka index is a distinguishing feature of git. See
349 <https://git.wiki.kernel.org/index.php/WhatIsTheIndex>`_ and
350 `IndexCommandQuickref
351 <https://git.wiki.kernel.org/index.php/IndexCommandQuickref>`_ in Git
362 Git has a builtin strategy for what Python core developers call
365 $ git merge -s ours v1 # null-merge v1 into v2
371 https://git-scm.com/book/en/Git-Tools-Rerere
374 Advanced configuration
375 ======================
380 Git has builtin mechanisms to handle line endings.
382 TODO: describe crlf configuration and .gitattributes.
388 TODO: dangling objects, git gc, git repack.
394 TODO: bash/zsh completion, bash/zsh prompt.
397 From Mercurial to git
398 =====================
400 Mercurial for Git users https://mercurial.selenic.com/wiki/GitConcepts
402 https://github.com/felipec/git-remote-hg
404 https://hg-git.github.io/
416 This document has been placed in the public domain.
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