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>`_.
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 have
105 done something like that::
107 $ git clone -b v2 http://git.python.org/python.git
109 $ git branch v1 origin/v1
111 The last command creates a new local branch v1 and sets
112 remotes/origin/v1 as its upstream remote branch.
114 The same result can achieved with commands::
116 $ git clone -b v1 http://git.python.org/python.git
118 $ git checkout --track origin/v2
120 The last command creates a new local branch v2, sets
121 remotes/origin/v2 as its upstream remote branch and checks it out into
122 the working directory.
125 Branches and branches
126 =====================
128 Git terminology can be a bit misleading. Take, for example, the term
129 "branch". In git it has two meanings. A branch is a directed line of
130 commits (possibly with merges). And a branch is a label or a pointer
131 assigned to a line of commits. It is important to differentiate when
132 you talk about commits and when about their labels. Lines of commits
133 are by itself unnamed and are usually only lengthening and merging.
134 Labels, on the other hand, can be created, moved, renamed and deleted
138 Remote repository and remote branches
139 =====================================
141 Another example of slightly misleading terminology. Remote
142 repositories are really remote, you access them via network (well, a
143 remote repository can be on your local disk, but it's still remote
144 because it's not the current repo).
146 Remote branches, on the other hand, are branches (pointers to commits)
147 in your local repository. They are there for you to remember what
148 branches and commits have been pulled from and pushed to what remote
149 repos (you can pull from and push to many remotes). Remote branches
150 live under ``remotes/REMOTE`` namespaces, e.g. ``remotes/origin/v2``.
152 To see the status of remote branches run::
156 To see local and remote branches (and tags) pointing to commits::
160 You never do your own development on remote branches. You create a
161 local branch that has a remote branch as upstream and do development
162 on that local branch. On push git updates remote branches, and on pull
163 git updates remote branches and fast-forwards, merges or rebases local
166 When you do an initial clone like this::
168 $ git clone -b v1 http://git.python.org/python.git
170 git clones remote repository ``http://git.python.org/python.git`` to
171 directory ``python``, creates remote branches and checks out branch
172 ``v1`` into the working directory.
174 Updating local and remote branches
175 ----------------------------------
177 There is a major difference between
181 $ git fetch REMOTE BRANCH
187 $ git fetch REMOTE BRANCH:BRANCH
189 The first command fetches commits from the named BRANCH in the REMOTE
190 repository that are not in your repository and leaves the id (the
191 hash) of the head commit in file .git/FETCH_HEAD. But it doesn't
192 update any branch (doesn't move any pointer).
194 The second command fetches commits from the named BRANCH in the REMOTE
195 repository that are not in your repository and updates both the local
196 branch BRANCH and its upstream remote branch. But it refuses to update
197 branches in case of non-fast-forward. And it refuses to update the
200 The first command is used internally by ``git pull``.
204 $ git pull REMOTE BRANCH
210 $ git fetch REMOTE BRANCH
211 $ git merge FETCH_HEAD # FETCH_HEAD is a literal here
213 Certainly, BRANCH in that case should be your current branch. If you
214 want to merge a different branch into your current branch first update
215 that non-current branch and then merge::
217 $ git fetch origin v1:v1 # Update v1
218 $ git pull --rebase origin v2 # Update the current branch v2 using
219 # rebase instead of merge
222 It is possible to configure git to make it fetch/pull a few branches
223 or all branches at once, so you can simply run
238 Pushing is a bit simpler. There is only one command ``push``. When you
243 $ git push origin v1 v2
245 git guesses (knowing upstream remote branches) that you really want
249 $ git push origin v1:v1 v2:v2
251 Git pushes commits to the remote repo and updates remote branches. Git
252 refuses to push commits that aren't fast-forwardable. You can
253 force-push anyway, but please remember - you can force-push to your
254 own repositories but don't force-push to public or shared repos. If
255 you find git refuses to push commits that aren't fast-forwardable,
256 better fetch and merge commits from the remote repo (or rebase your
257 commits on top of the fetched commits), then push. Only force-push if
258 you know what you do and why you do it. See the section `Commit
259 editing and caveats`_ below.
261 It is possible to configure git to make it push a few branches or all
262 branches at once, so you can simply run
274 Git refuses to push a branch if it's the current branch in the remote
275 non-bare repository: git refuses to update remote working directory.
276 You really should push only to bare repositories. For non-bare
277 repositories git prefers pull-based workflow.
282 Git automatically fetches tags that point to commits being fetched
283 during fetch/pull. To fetch all tags (and commits they point to) run
284 ``git fetch --tags origin``. To fetch some specific tags fetch them
287 $ git fetch origin tag NAME1 tag NAME2...
291 $ git fetch origin tag 1.4.2 tag 2.1.7
293 Git doesn't automatically pushes tags. That allows you to have private
294 tags (lightweight tags are also private for a repo, they cannot be
295 pushed). To push tag(s) list them explicitly::
297 $ git push origin tag 1.4.2
298 $ git push origin v1 v2 tag 2.1.7
301 Commit editing and caveats
302 ==========================
304 A warning not to edit published (pushed) commits also appears in
305 documentation but it's repeated here anyway as it's very important.
307 It is possible to recover from forced push but it's PITA for the
308 entire team. Please avoid it.
310 To see what commits have not been published yet compare the head of the
311 branch with its upstream remote branch::
313 $ git log origin/v2..
314 $ git log origin/v1..v1
316 For every branch that has an upstream remote branch git maintains an
317 alias @{upstream} (short version @{u}), so the commands above can be
323 To see the status of all branches::
327 To compare the status of local branches with a remote repo::
329 $ git remote show origin
331 Read `how to recover from upstream rebase
332 <https://git-scm.com/docs/git-rebase#_recovering_from_upstream_rebase>`_.
333 It is in ``git help rebase``.
335 On the other hand don't be too afraid about commit editing. You can
336 safely edit, remove, reorder, combine and split commits that hasn't
337 been pushed yet. You can even push commits to your own (backup) repo,
338 edit them later and force-push edited commits to replace what has
339 already been pushed. Not a problem until commits are in a public
340 or shared repository.
346 TODO: describe undo strategies: git reset, git revert, git checkout,
347 git reflog. "Commit early, commit often".
350 https://kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html
359 Staging area aka index is a distinguishing feature of git. See
361 <https://git.wiki.kernel.org/index.php/WhatIsTheIndex>`_ and
362 `IndexCommandQuickref
363 <https://git.wiki.kernel.org/index.php/IndexCommandQuickref>`_ in Git
374 Git has a builtin strategy for what Python core developers call
377 $ git merge -s ours v1 # null-merge v1 into v2
383 https://git-scm.com/book/en/Git-Tools-Rerere
386 Advanced configuration
387 ======================
392 Git has builtin mechanisms to handle line endings.
394 TODO: describe crlf configuration and .gitattributes.
400 TODO: dangling objects, git gc, git repack.
406 TODO: bash/zsh completion, bash/zsh prompt.
409 From Mercurial to git
410 =====================
412 Mercurial for Git users https://mercurial.selenic.com/wiki/GitConcepts
414 https://github.com/felipec/git-remote-hg
416 https://hg-git.github.io/
428 This document has been placed in the public domain.
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