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>`_.
48 Advanced documentation
49 ----------------------
52 <http://www-cs-students.stanford.edu/~blynn/gitmagic/index.html>`_,
53 also with a number of translations.
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 `git-cola <https://git-cola.github.io/index.html>`_ is a sleek and
89 powerful Git GUI written in Python and GPL licensed. Linux, Windows,
92 `TortoiseGit <https://tortoisegit.org/>`_ is a Windows Shell Interface
93 to Git based on TortoiseSVN; open source.
98 This simple code is often appears in documentation, but it is
99 important so let repeat it here. Git stores author and committer
100 names/emails in every commit, so configure your real name and
103 $ git config --global user.name "User Name"
104 $ git config --global user.email user.name@example.org
110 Examples of git commands in this PEP use the following approach. It is
111 supposed that you, the user, works with a local repository named
112 ``python`` that has an upstream remote repo named ``origin``. Your
113 local repo has two branches ``v1`` and ``v2``. For most examples the
114 currently checked out branch is ``v2``. That is, it's assumed you have
115 done something like that::
117 $ git clone -b v2 http://git.python.org/python.git
119 $ git branch v1 origin/v1
121 The first command clones remote repository into local directory
122 `python``, creates a new local branch v2, sets remotes/origin/v2 as
123 its upstream remote branch and checks it out into the working
126 The last command creates a new local branch v1 and sets
127 remotes/origin/v1 as its upstream remote branch.
129 The same result can be achieved with commands::
131 $ git clone -b v1 http://git.python.org/python.git
133 $ git checkout --track origin/v2
135 The last command creates a new local branch v2, sets
136 remotes/origin/v2 as its upstream remote branch and checks it out into
137 the working directory.
140 Branches and branches
141 =====================
143 Git terminology can be a bit misleading. Take, for example, the term
144 "branch". In git it has two meanings. A branch is a directed line of
145 commits (possibly with merges). And a branch is a label or a pointer
146 assigned to a line of commits. It is important to differentiate when
147 you talk about commits and when about their labels. Lines of commits
148 are by itself unnamed and are usually only lengthening and merging.
149 Labels, on the other hand, can be created, moved, renamed and deleted
153 Remote repository and remote branches
154 =====================================
156 Another example of slightly misleading terminology. Remote
157 repositories are really remote, you access them via network (well, a
158 remote repository can be on your local disk, but it's still remote
159 because it's not the current repo).
161 Remote branches, on the other hand, are branches (pointers to commits)
162 in your local repository. They are there for you to remember what
163 branches and commits have been pulled from and pushed to what remote
164 repos (you can pull from and push to many remotes). Remote branches
165 live under ``remotes/REMOTE`` namespaces, e.g. ``remotes/origin/v2``.
167 To see the status of remote branches run::
171 To see local and remote branches (and tags) pointing to commits::
175 You never do your own development on remote branches. You create a
176 local branch that has a remote branch as upstream and do development
177 on that local branch. On push git updates remote branches, and on pull
178 git updates remote branches and fast-forwards, merges or rebases local
181 When you do an initial clone like this::
183 $ git clone -b v1 http://git.python.org/python.git
185 git clones remote repository ``http://git.python.org/python.git`` to
186 directory ``python``, creates remote branches, creates a local branch
187 ``v1``, configure it to track upstream remotes/origin/v1 branch and
188 checks out ``v1`` into the working directory.
190 Updating local and remote branches
191 ----------------------------------
193 There is a major difference between
197 $ git fetch REMOTE BRANCH
203 $ git fetch REMOTE BRANCH:BRANCH
205 The first command fetches commits from the named BRANCH in the REMOTE
206 repository that are not in your repository and leaves the id (the
207 hash) of the head commit in file .git/FETCH_HEAD. But it doesn't
208 update any branch (doesn't move any pointer).
210 The second command fetches commits from the named BRANCH in the REMOTE
211 repository that are not in your repository and updates both the local
212 branch BRANCH and its upstream remote branch. But it refuses to update
213 branches in case of non-fast-forward. And it refuses to update the
216 The first command is used internally by ``git pull``.
220 $ git pull REMOTE BRANCH
226 $ git fetch REMOTE BRANCH
227 $ git merge FETCH_HEAD # FETCH_HEAD is a literal here
229 Certainly, BRANCH in that case should be your current branch. If you
230 want to merge a different branch into your current branch first update
231 that non-current branch and then merge::
233 $ git fetch origin v1:v1 # Update v1
234 $ git pull --rebase origin v2 # Update the current branch v2 using
235 # rebase instead of merge
238 If you have not yet pushed commits on ``v1``, though, the scenario has
239 to become a bit more complex. Git refuses to update
240 non-fast-forwardable branch, and you don't want to do force-pull
241 because that would remove your non-pushed commits and you would need
242 to recover. So you want to rebase ``v1`` but you cannot rebase
243 non-current branch. Hence, checkout ``v1`` and rebase it before
247 $ git pull --rebase origin v1
249 $ git pull --rebase origin v2
252 It is possible to configure git to make it fetch/pull a few branches
253 or all branches at once, so you can simply run
268 Pushing is a bit simpler. There is only one command ``push``. When you
273 $ git push origin v1 v2
275 git guesses (knowing upstream remote branches) that you really want
279 $ git push origin v1:v1 v2:v2
281 Git pushes commits to the remote repo and updates remote branches. Git
282 refuses to push commits that aren't fast-forwardable. You can
283 force-push anyway, but please remember - you can force-push to your
284 own repositories but don't force-push to public or shared repos. If
285 you find git refuses to push commits that aren't fast-forwardable,
286 better fetch and merge commits from the remote repo (or rebase your
287 commits on top of the fetched commits), then push. Only force-push if
288 you know what you do and why you do it. See the section `Commit
289 editing and caveats`_ below.
291 It is possible to configure git to make it push a few branches or all
292 branches at once, so you can simply run
304 Git refuses to push a branch if it's the current branch in the remote
305 non-bare repository: git refuses to update remote working directory.
306 You really should push only to bare repositories. For non-bare
307 repositories git prefers pull-based workflow.
309 When you want to deploy code on a remote host and can only use push
310 (because your workstation is behind a firewall and you cannot pull
311 from it) you do that in two steps using two repositories: you push
312 from the workstation to a bare repo on the remote host, ssh to the
313 remote host and pull from the bare repo to a non-bare deployment repo.
318 Git automatically fetches tags that point to commits being fetched
319 during fetch/pull. To fetch all tags (and commits they point to) run
320 ``git fetch --tags origin``. To fetch some specific tags fetch them
323 $ git fetch origin tag TAG1 tag TAG2...
327 $ git fetch origin tag 1.4.2 tag 2.1.7
329 Git doesn't automatically pushes tags. That allows you to have private
330 tags (lightweight tags are also private for a repo, they cannot be
331 pushed). To push tags list them explicitly::
333 $ git push origin tag 1.4.2
334 $ git push origin v1 v2 tag 2.1.7
336 Don't move tags with ``git tag -f`` after they have been published.
339 Commit editing and caveats
340 ==========================
342 A warning not to edit published (pushed) commits also appears in
343 documentation but it's repeated here anyway as it's very important.
345 It is possible to recover from forced push but it's PITA for the
346 entire team. Please avoid it.
348 To see what commits have not been published yet compare the head of the
349 branch with its upstream remote branch::
351 $ git log origin/v2..
352 $ git log origin/v1..v1
354 For every branch that has an upstream remote branch git maintains an
355 alias @{upstream} (short version @{u}), so the commands above can be
361 To see the status of all branches::
365 To compare the status of local branches with a remote repo::
367 $ git remote show origin
369 Read `how to recover from upstream rebase
370 <https://git-scm.com/docs/git-rebase#_recovering_from_upstream_rebase>`_.
371 It is in ``git help rebase``.
373 On the other hand don't be too afraid about commit editing. You can
374 safely edit, remove, reorder, combine and split commits that hasn't
375 been pushed yet. You can even push commits to your own (backup) repo,
376 edit them later and force-push edited commits to replace what has
377 already been pushed. Not a problem until commits are in a public
378 or shared repository.
384 TODO: describe undo strategies: git reset, git revert, git checkout,
385 git reflog. "Commit early, commit often".
388 https://www.kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html
394 Internet is full of heated discussions on the topic: "merge or
395 rebase?" Most of them are meaningless. When a DVCS is being used in a
396 big team with a big and complex project with many branches there is
397 simply no way to avoid merges. So the question's diminished to
398 "whether to use rebase, and if yes - when to use rebase?" Considering
399 that it is very much recommended not to rebase published commits the
400 question's diminished even further: "whether to use rebase on
403 That small question is for the team to decide. The author of the PEP
404 recommends to use rebase when pulling, i.e. always do ``git pull
405 --rebase`` or even configure automatic setup of rebase for every new
408 $ git config branch.autosetuprebase true
410 and configure rebase for existing branches::
412 $ git config branch.NAME.rebase true
416 $ git config branch.v1.rebase true
417 $ git config branch.v2.rebase true
419 After that ``git pull origin v2`` becomes equivalent to ``git pull
420 --rebase origin v2``.
422 In case when merge is preferred it is recommended to create new
423 commits in a separate feature or topic branch while using rebase to
424 update the mainline branch. When the topic branch is ready merge it
425 into mainline. To avoid a tedious task of resolving large number of
426 conflicts at once you can merge the topic branch to the mainline from
427 time to time and switch back to the topic branch to continue working
428 on it. The entire workflow would be something like::
430 $ git checkout -b issue-42 # create and switch to a new branch
431 ...edit/test/commit...
433 $ git pull --rebase origin v2 # update v2 from the upstream
435 $ git branch -d issue-42 # delete the topic branch
438 When the topic branch is deleted only the label is removed, commits
439 are stayed in the database, they are now merged into v2::
441 o--o--o--o--o--M--< v2 - the mainline branch
443 --*--*--* - the topic branch, now unnamed
445 The topic branch is deleted to avoid cluttering branch namespace with
446 small topic branches. Information on what issue was fixed or what
447 feature was implemented should be in the commit messages.
453 Git has a builtin strategy for what Python core developers call
456 $ git merge -s ours v1 # null-merge v1 into v2
462 https://git-scm.com/book/en/Git-Tools-Rerere
471 Staging area aka index is a distinguishing feature of git. See
473 <https://git.wiki.kernel.org/index.php/WhatIsTheIndex>`_ and
474 `IndexCommandQuickref
475 <https://git.wiki.kernel.org/index.php/IndexCommandQuickref>`_ in Git
479 Advanced configuration
480 ======================
485 Git has builtin mechanisms to handle line endings.
487 TODO: describe crlf configuration and .gitattributes.
493 TODO: dangling objects, git gc, git repack.
494 https://gcc.gnu.org/ml/gcc/2007-12/msg00165.html
500 TODO: sticky options; example: git grep -O.
502 TODO: tricky options; example: git log -p3.
504 TODO: bash/zsh completion, bash/zsh prompt.
505 https://git.kernel.org/cgit/git/git.git/tree/contrib/completion
511 TODO: anonymous access; git over ssh; gitolite; gitweb; cgit; gitlab.
513 http://gitolite.com/gitolite/index.html
515 https://git.kernel.org/cgit/git/git.git/tree/gitweb
517 http://git.zx2c4.com/cgit/
519 From Mercurial to git
520 =====================
522 Mercurial for Git users https://mercurial.selenic.com/wiki/GitConcepts
524 https://github.com/felipec/git-remote-hg
526 https://hg-git.github.io/
538 This document has been placed in the public domain.
545 indent-tabs-mode: nil
546 sentence-end-double-space: t
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