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 from
83 `MacPorts <https://www.macports.org/ports.php?by=name&substr=git>`_ or
85 <http://sourceforge.net/projects/git-osx-installer/files/>`_ or
86 install git with `Homebrew <http://brew.sh/>`_: ``brew install git``.
91 This simple code is often appears in documentation, but it is
92 important so let repeat it here. Git stores author and committer
93 names/emails in every commit, so configure your real name and
96 $ git config --global user.name "User Name"
97 $ git config --global user.email user.name@example.org
103 Examples of git commands in this PEP use the following approach. It is
104 supposed that you, the user, works with a local repository named
105 ``python`` that has an upstream remote repo named ``origin``. Your
106 local repo has two branches ``v1`` and ``v2``. For most examples the
107 currently checked out branch is ``v2``. That is, it's assumed you have
108 done something like that::
110 $ git clone -b v2 http://git.python.org/python.git
112 $ git branch v1 origin/v1
114 The last command creates a new local branch v1 and sets
115 remotes/origin/v1 as its upstream remote branch.
117 The same result can achieved with commands::
119 $ git clone -b v1 http://git.python.org/python.git
121 $ git checkout --track origin/v2
123 The last command creates a new local branch v2, sets
124 remotes/origin/v2 as its upstream remote branch and checks it out into
125 the working directory.
128 Branches and branches
129 =====================
131 Git terminology can be a bit misleading. Take, for example, the term
132 "branch". In git it has two meanings. A branch is a directed line of
133 commits (possibly with merges). And a branch is a label or a pointer
134 assigned to a line of commits. It is important to differentiate when
135 you talk about commits and when about their labels. Lines of commits
136 are by itself unnamed and are usually only lengthening and merging.
137 Labels, on the other hand, can be created, moved, renamed and deleted
141 Remote repository and remote branches
142 =====================================
144 Another example of slightly misleading terminology. Remote
145 repositories are really remote, you access them via network (well, a
146 remote repository can be on your local disk, but it's still remote
147 because it's not the current repo).
149 Remote branches, on the other hand, are branches (pointers to commits)
150 in your local repository. They are there for you to remember what
151 branches and commits have been pulled from and pushed to what remote
152 repos (you can pull from and push to many remotes). Remote branches
153 live under ``remotes/REMOTE`` namespaces, e.g. ``remotes/origin/v2``.
155 To see the status of remote branches run::
159 To see local and remote branches (and tags) pointing to commits::
163 You never do your own development on remote branches. You create a
164 local branch that has a remote branch as upstream and do development
165 on that local branch. On push git updates remote branches, and on pull
166 git updates remote branches and fast-forwards, merges or rebases local
169 When you do an initial clone like this::
171 $ git clone -b v1 http://git.python.org/python.git
173 git clones remote repository ``http://git.python.org/python.git`` to
174 directory ``python``, creates remote branches, creates a local branch
175 ``v1``, configure it to track upstream remotes/origin/v1 branch and
176 checks out ``v1`` into the working directory.
178 Updating local and remote branches
179 ----------------------------------
181 There is a major difference between
185 $ git fetch REMOTE BRANCH
191 $ git fetch REMOTE BRANCH:BRANCH
193 The first command fetches commits from the named BRANCH in the REMOTE
194 repository that are not in your repository and leaves the id (the
195 hash) of the head commit in file .git/FETCH_HEAD. But it doesn't
196 update any branch (doesn't move any pointer).
198 The second command fetches commits from the named BRANCH in the REMOTE
199 repository that are not in your repository and updates both the local
200 branch BRANCH and its upstream remote branch. But it refuses to update
201 branches in case of non-fast-forward. And it refuses to update the
204 The first command is used internally by ``git pull``.
208 $ git pull REMOTE BRANCH
214 $ git fetch REMOTE BRANCH
215 $ git merge FETCH_HEAD # FETCH_HEAD is a literal here
217 Certainly, BRANCH in that case should be your current branch. If you
218 want to merge a different branch into your current branch first update
219 that non-current branch and then merge::
221 $ git fetch origin v1:v1 # Update v1
222 $ git pull --rebase origin v2 # Update the current branch v2 using
223 # rebase instead of merge
226 If you have not yet pushed commits on ``v1``, though, the scenario has
227 to become a bit more complex. Git refuses to update
228 non-fast-forwardable branch, and you don't want to do force-pull
229 because that would remove your non-pushed commits and you would need
230 to recover. So you want to rebase ``v1`` but you cannot rebase
231 non-current branch. Hence, checkout ``v1`` and rebase it before
235 $ git pull --rebase origin v1
237 $ git pull --rebase origin v2
240 It is possible to configure git to make it fetch/pull a few branches
241 or all branches at once, so you can simply run
256 Pushing is a bit simpler. There is only one command ``push``. When you
261 $ git push origin v1 v2
263 git guesses (knowing upstream remote branches) that you really want
267 $ git push origin v1:v1 v2:v2
269 Git pushes commits to the remote repo and updates remote branches. Git
270 refuses to push commits that aren't fast-forwardable. You can
271 force-push anyway, but please remember - you can force-push to your
272 own repositories but don't force-push to public or shared repos. If
273 you find git refuses to push commits that aren't fast-forwardable,
274 better fetch and merge commits from the remote repo (or rebase your
275 commits on top of the fetched commits), then push. Only force-push if
276 you know what you do and why you do it. See the section `Commit
277 editing and caveats`_ below.
279 It is possible to configure git to make it push a few branches or all
280 branches at once, so you can simply run
292 Git refuses to push a branch if it's the current branch in the remote
293 non-bare repository: git refuses to update remote working directory.
294 You really should push only to bare repositories. For non-bare
295 repositories git prefers pull-based workflow.
297 When you want to deploy code on a remote host and can only use push
298 (because your workstation is behind a firewall and you cannot pull
299 from it) you do that in two steps using two repositories: you push
300 from the workstation to a bare repo on the remote host, ssh to the
301 remote host and pull from the bare repo to a non-bare deployment repo.
306 Git automatically fetches tags that point to commits being fetched
307 during fetch/pull. To fetch all tags (and commits they point to) run
308 ``git fetch --tags origin``. To fetch some specific tags fetch them
311 $ git fetch origin tag TAG1 tag TAG2...
315 $ git fetch origin tag 1.4.2 tag 2.1.7
317 Git doesn't automatically pushes tags. That allows you to have private
318 tags (lightweight tags are also private for a repo, they cannot be
319 pushed). To push tags list them explicitly::
321 $ git push origin tag 1.4.2
322 $ git push origin v1 v2 tag 2.1.7
324 Don't move tags with ``git tag -f`` after they have been published.
327 Commit editing and caveats
328 ==========================
330 A warning not to edit published (pushed) commits also appears in
331 documentation but it's repeated here anyway as it's very important.
333 It is possible to recover from forced push but it's PITA for the
334 entire team. Please avoid it.
336 To see what commits have not been published yet compare the head of the
337 branch with its upstream remote branch::
339 $ git log origin/v2..
340 $ git log origin/v1..v1
342 For every branch that has an upstream remote branch git maintains an
343 alias @{upstream} (short version @{u}), so the commands above can be
349 To see the status of all branches::
353 To compare the status of local branches with a remote repo::
355 $ git remote show origin
357 Read `how to recover from upstream rebase
358 <https://git-scm.com/docs/git-rebase#_recovering_from_upstream_rebase>`_.
359 It is in ``git help rebase``.
361 On the other hand don't be too afraid about commit editing. You can
362 safely edit, remove, reorder, combine and split commits that hasn't
363 been pushed yet. You can even push commits to your own (backup) repo,
364 edit them later and force-push edited commits to replace what has
365 already been pushed. Not a problem until commits are in a public
366 or shared repository.
372 TODO: describe undo strategies: git reset, git revert, git checkout,
373 git reflog. "Commit early, commit often".
376 https://kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html
386 Git has a builtin strategy for what Python core developers call
389 $ git merge -s ours v1 # null-merge v1 into v2
395 https://git-scm.com/book/en/Git-Tools-Rerere
404 Staging area aka index is a distinguishing feature of git. See
406 <https://git.wiki.kernel.org/index.php/WhatIsTheIndex>`_ and
407 `IndexCommandQuickref
408 <https://git.wiki.kernel.org/index.php/IndexCommandQuickref>`_ in Git
412 Advanced configuration
413 ======================
418 Git has builtin mechanisms to handle line endings.
420 TODO: describe crlf configuration and .gitattributes.
426 TODO: dangling objects, git gc, git repack.
432 TODO: sticky options; example: git grep -O.
434 TODO: bash/zsh completion, bash/zsh prompt.
440 TODO: anonymous access; git over ssh; gitolite; gitweb; cgit; gitlab.
443 From Mercurial to git
444 =====================
446 Mercurial for Git users https://mercurial.selenic.com/wiki/GitConcepts
448 https://github.com/felipec/git-remote-hg
450 https://hg-git.github.io/
462 This document has been placed in the public domain.
469 indent-tabs-mode: nil
470 sentence-end-double-space: t
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