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``.
88 `Atlassins's SourceTree <https://www.sourcetreeapp.com/>`_ is a free
89 Git and Mercurial GUI client for Windows or Mac.
94 This simple code is often appears in documentation, but it is
95 important so let repeat it here. Git marks every commit with author
96 and committer names/emails, so configure your real name and preferred
99 $ git config --global user.name "User Name"
100 $ git config --global user.email user.name@example.org
106 Examples of git commands in this PEP use the following approach. It is
107 supposed that you, the user, works with a local repository named
108 ``python`` that has an upstream remote repo named ``origin``. Your
109 local repo has two branches ``v1`` and ``v2``. For most examples the
110 currently checked out branch is ``v2``. That is, it's assumed you have
111 done something like that::
113 $ git clone -b v2 http://git.python.org/python.git
115 $ git branch v1 origin/v1
117 The last command creates a new local branch v1 and sets
118 remotes/origin/v1 as its upstream remote branch.
120 The same result can achieved with commands::
122 $ git clone -b v1 http://git.python.org/python.git
124 $ git checkout --track origin/v2
126 The last command creates a new local branch v2, sets
127 remotes/origin/v2 as its upstream remote branch and checks it out into
128 the working directory.
131 Branches and branches
132 =====================
134 Git terminology can be a bit misleading. Take, for example, the term
135 "branch". In git it has two meanings. A branch is a directed line of
136 commits (possibly with merges). And a branch is a label or a pointer
137 assigned to a line of commits. It is important to differentiate when
138 you talk about commits and when about their labels. Lines of commits
139 are by itself unnamed and are usually only lengthening and merging.
140 Labels, on the other hand, can be created, moved, renamed and deleted
144 Remote repository and remote branches
145 =====================================
147 Another example of slightly misleading terminology. Remote
148 repositories are really remote, you access them via network (well, a
149 remote repository can be on your local disk, but it's still remote
150 because it's not the current repo).
152 Remote branches, on the other hand, are branches (pointers to commits)
153 in your local repository. They are there for you to remember what
154 branches and commits have been pulled from and pushed to what remote
155 repos (you can pull from and push to many remotes). Remote branches
156 live under ``remotes/REMOTE`` namespaces, e.g. ``remotes/origin/v2``.
158 To see the status of remote branches run::
162 To see local and remote branches (and tags) pointing to commits::
166 You never do your own development on remote branches. You create a
167 local branch that has a remote branch as upstream and do development
168 on that local branch. On push git updates remote branches, and on pull
169 git updates remote branches and fast-forwards, merges or rebases local
172 When you do an initial clone like this::
174 $ git clone -b v1 http://git.python.org/python.git
176 git clones remote repository ``http://git.python.org/python.git`` to
177 directory ``python``, creates remote branches, creates a local branch
178 ``v1``, configure it to track upstream remotes/origin/v1 branch and
179 checks out ``v1`` into the working directory.
181 Updating local and remote branches
182 ----------------------------------
184 There is a major difference between
188 $ git fetch REMOTE BRANCH
194 $ git fetch REMOTE BRANCH:BRANCH
196 The first command fetches commits from the named BRANCH in the REMOTE
197 repository that are not in your repository and leaves the id (the
198 hash) of the head commit in file .git/FETCH_HEAD. But it doesn't
199 update any branch (doesn't move any pointer).
201 The second command fetches commits from the named BRANCH in the REMOTE
202 repository that are not in your repository and updates both the local
203 branch BRANCH and its upstream remote branch. But it refuses to update
204 branches in case of non-fast-forward. And it refuses to update the
207 The first command is used internally by ``git pull``.
211 $ git pull REMOTE BRANCH
217 $ git fetch REMOTE BRANCH
218 $ git merge FETCH_HEAD # FETCH_HEAD is a literal here
220 Certainly, BRANCH in that case should be your current branch. If you
221 want to merge a different branch into your current branch first update
222 that non-current branch and then merge::
224 $ git fetch origin v1:v1 # Update v1
225 $ git pull --rebase origin v2 # Update the current branch v2 using
226 # rebase instead of merge
229 If you have not yet pushed commits on ``v1``, though, the scenario has
230 to become a bit more complex. Git refuses to update
231 non-fast-forwardable branch, and you don't want to do force-pull
232 because that would remove your non-pushed commits and you would need
233 to recover. So you want to rebase ``v1`` but you cannot rebase
234 non-current branch. Hence, checkout ``v1`` and rebase it before
238 $ git pull --rebase origin v1
240 $ git pull --rebase origin v2
243 It is possible to configure git to make it fetch/pull a few branches
244 or all branches at once, so you can simply run
259 Pushing is a bit simpler. There is only one command ``push``. When you
264 $ git push origin v1 v2
266 git guesses (knowing upstream remote branches) that you really want
270 $ git push origin v1:v1 v2:v2
272 Git pushes commits to the remote repo and updates remote branches. Git
273 refuses to push commits that aren't fast-forwardable. You can
274 force-push anyway, but please remember - you can force-push to your
275 own repositories but don't force-push to public or shared repos. If
276 you find git refuses to push commits that aren't fast-forwardable,
277 better fetch and merge commits from the remote repo (or rebase your
278 commits on top of the fetched commits), then push. Only force-push if
279 you know what you do and why you do it. See the section `Commit
280 editing and caveats`_ below.
282 It is possible to configure git to make it push a few branches or all
283 branches at once, so you can simply run
295 Git refuses to push a branch if it's the current branch in the remote
296 non-bare repository: git refuses to update remote working directory.
297 You really should push only to bare repositories. For non-bare
298 repositories git prefers pull-based workflow.
300 When you want to deploy code on a remote host and can only use push
301 (because your workstation is behind a firewall and you cannot pull
302 from it) you do that in two steps using two repositories: you push
303 from the workstation to a bare repo on the remote host, ssh to the
304 remote host and pull from the bare repo to a non-bare deployment repo.
309 Git automatically fetches tags that point to commits being fetched
310 during fetch/pull. To fetch all tags (and commits they point to) run
311 ``git fetch --tags origin``. To fetch some specific tags fetch them
314 $ git fetch origin tag TAG1 tag TAG2...
318 $ git fetch origin tag 1.4.2 tag 2.1.7
320 Git doesn't automatically pushes tags. That allows you to have private
321 tags (lightweight tags are also private for a repo, they cannot be
322 pushed). To push tags list them explicitly::
324 $ git push origin tag 1.4.2
325 $ git push origin v1 v2 tag 2.1.7
327 Don't move tags with ``git tag -f`` after they have been published.
330 Commit editing and caveats
331 ==========================
333 A warning not to edit published (pushed) commits also appears in
334 documentation but it's repeated here anyway as it's very important.
336 It is possible to recover from forced push but it's PITA for the
337 entire team. Please avoid it.
339 To see what commits have not been published yet compare the head of the
340 branch with its upstream remote branch::
342 $ git log origin/v2..
343 $ git log origin/v1..v1
345 For every branch that has an upstream remote branch git maintains an
346 alias @{upstream} (short version @{u}), so the commands above can be
352 To see the status of all branches::
356 To compare the status of local branches with a remote repo::
358 $ git remote show origin
360 Read `how to recover from upstream rebase
361 <https://git-scm.com/docs/git-rebase#_recovering_from_upstream_rebase>`_.
362 It is in ``git help rebase``.
364 On the other hand don't be too afraid about commit editing. You can
365 safely edit, remove, reorder, combine and split commits that hasn't
366 been pushed yet. You can even push commits to your own (backup) repo,
367 edit them later and force-push edited commits to replace what has
368 already been pushed. Not a problem until commits are in a public
369 or shared repository.
375 TODO: describe undo strategies: git reset, git revert, git checkout,
376 git reflog. "Commit early, commit often".
379 https://kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html
389 Git has a builtin strategy for what Python core developers call
392 $ git merge -s ours v1 # null-merge v1 into v2
398 https://git-scm.com/book/en/Git-Tools-Rerere
407 Staging area aka index is a distinguishing feature of git. See
409 <https://git.wiki.kernel.org/index.php/WhatIsTheIndex>`_ and
410 `IndexCommandQuickref
411 <https://git.wiki.kernel.org/index.php/IndexCommandQuickref>`_ in Git
415 Advanced configuration
416 ======================
421 Git has builtin mechanisms to handle line endings.
423 TODO: describe crlf configuration and .gitattributes.
429 TODO: dangling objects, git gc, git repack.
435 TODO: sticky options; example: git grep -O.
437 TODO: bash/zsh completion, bash/zsh prompt.
443 TODO: anonymous access; git over ssh; gitolite; gitweb; cgit; gitlab.
446 From Mercurial to git
447 =====================
449 Mercurial for Git users https://mercurial.selenic.com/wiki/GitConcepts
451 https://github.com/felipec/git-remote-hg
453 https://hg-git.github.io/
465 This document has been placed in the public domain.
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