`Git Magic
<http://www-cs-students.stanford.edu/~blynn/gitmagic/index.html>`_,
-also with a number of translations.
+with a number of translations.
`Pro Git <https://git-scm.com/book>`_. The Book about git. Buy it at
Amazon or download in PDF, mobi, or ePub form. Has translations to
Download and installation
-------------------------
-Unix users: download and install using your package manager.
+Unix users: `download and install using your package manager
+<https://git-scm.com/download/linux>`_.
Microsoft Windows: download `git-for-windows
<https://github.com/git-for-windows/git/releases>`_ or `msysGit
Examples of git commands in this PEP use the following approach. It is
supposed that you, the user, works with a local repository named
``python`` that has an upstream remote repo named ``origin``. Your
-local repo has two branches ``v1`` and ``v2``. For most examples the
-currently checked out branch is ``v2``. That is, it's assumed you have
-done something like that::
+local repo has two branches ``v1`` and ``master``. For most examples
+the currently checked out branch is ``master``. That is, it's assumed
+you have done something like that::
- $ git clone -b v2 http://git.python.org/python.git
+ $ git clone http://git.python.org/python.git
$ cd python
$ git branch v1 origin/v1
The first command clones remote repository into local directory
-`python``, creates a new local branch v2, sets remotes/origin/v2 as
-its upstream remote-tracking branch and checks it out into the working
-directory.
+`python``, creates a new local branch master, sets
+remotes/origin/master as its upstream remote-tracking branch and
+checks it out into the working directory.
The last command creates a new local branch v1 and sets
remotes/origin/v1 as its upstream remote-tracking branch.
$ git clone -b v1 http://git.python.org/python.git
$ cd python
- $ git checkout --track origin/v2
+ $ git checkout --track origin/master
-The last command creates a new local branch v2, sets remotes/origin/v2
-as its upstream remote-tracking branch and checks it out into the
-working directory.
+The last command creates a new local branch master, sets
+remotes/origin/master as its upstream remote-tracking branch and
+checks it out into the working directory.
Branches and branches
local repository. They are there for you to remember what branches and
commits have been pulled from and pushed to what remote repos (you can
pull from and push to many remotes). Remote-tracking branches live
-under ``remotes/$REMOTE`` namespaces, e.g. ``remotes/origin/v2``.
+under ``remotes/$REMOTE`` namespaces, e.g. ``remotes/origin/master``.
To see the status of remote-tracking branches run::
$ git fetch $REMOTE $BRANCH:$BRANCH
The first command fetches commits from the named $BRANCH in the
-$REMOTE repository that are not in your repository and leaves the id
-(the hash) of the head commit in file .git/FETCH_HEAD and updates
-remote-tracking branch.
+$REMOTE repository that are not in your repository, updates
+remote-tracking branch and leaves the id (the hash) of the head commit
+in file .git/FETCH_HEAD.
The second command fetches commits from the named $BRANCH in the
$REMOTE repository that are not in your repository and updates both
that non-current branch and then merge::
$ git fetch origin v1:v1 # Update v1
- $ git pull --rebase origin v2 # Update the current branch v2 using
- # rebase instead of merge
+ $ git pull --rebase origin master # Update the current branch master
+ # using rebase instead of merge
$ git merge v1
If you have not yet pushed commits on ``v1``, though, the scenario has
$ git checkout v1
$ git pull --rebase origin v1
- $ git checkout v2
- $ git pull --rebase origin v2
+ $ git checkout master
+ $ git pull --rebase origin master
$ git merge v1
It is possible to configure git to make it fetch/pull a few branches
::
- $ git push origin v1 v2
+ $ git push origin v1 master
-git pushes local v1 to remote v1 and local v2 to remote v2. The same
-as::
+git pushes local v1 to remote v1 and local master to remote master.
+The same as::
- $ git push origin v1:v1 v2:v2
+ $ git push origin v1:v1 master:master
Git pushes commits to the remote repo and updates remote-tracking
branches. Git refuses to push commits that aren't fast-forwardable.
from the workstation to a bare repo on the remote host, ssh to the
remote host and pull from the bare repo to a non-bare deployment repo.
+That changed in git 2.3, but see `the blog post
+<https://github.com/blog/1957-git-2-3-has-been-released#push-to-deploy>`_
+for caveats; in 2.4 the push-to-deploy feature was `further improved
+<https://github.com/blog/1994-git-2-4-atomic-pushes-push-to-deploy-and-more#push-to-deploy-improvements>`_.
+
Tags
''''
For example::
- $ git fetch origin tag 1.4.2 tag 2.1.7
+ $ git fetch origin tag 1.4.2
+ $ git fetch origin v1:v1 tag 2.1.7
Git doesn't automatically pushes tags. That allows you to have private
-tags (lightweight tags are also private for a repo, they cannot be
-pushed). To push tags list them explicitly::
+tags. To push tags list them explicitly::
$ git push origin tag 1.4.2
- $ git push origin v1 v2 tag 2.1.7
+ $ git push origin v1 master tag 2.1.7
Don't move tags with ``git tag -f`` or remove tags with ``git tag -d``
after they have been published.
+Private information
+'''''''''''''''''''
+
+When cloning/fetching/pulling/pushing git copies only database objects
+(commits, trees, files and tags) and symbolic references (branches and
+lightweight tags). Everything else is private to the repository and
+never cloned, updated or pushed. It's your config, your hooks, your
+private exclude file.
+
+If you want to distribute hooks, copy them to the working tree, add,
+commit, push and instruct the team to update ind install the hook
+manually.
+
Commit editing and caveats
==========================
To see what commits have not been published yet compare the head of the
branch with its upstream remote-tracking branch::
- $ git log origin/v2..
+ $ git log origin/master..
$ git log origin/v1..v1
For every branch that has an upstream remote-tracking branch git
It is in ``git help rebase``.
On the other hand don't be too afraid about commit editing. You can
-safely edit, remove, reorder, combine and split commits that hasn't
+safely edit, remove, reorder, combine and split commits that haven't
been pushed yet. You can even push commits to your own (backup) repo,
-edit them later and force-push edited commits to replace what has
+edit them later and force-push edited commits to replace what have
already been pushed. Not a problem until commits are in a public
or shared repository.
git reflog: reference log
-------------------------
+Removing commits with ``git reset`` or moving the head of a branch
+sounds dangerous and it is. But there is a way to undo: another
+reset back to the original commit. Git doesn't remove commits
+immediately; unreferenced commits (in git terminology they are called
+"dangling commits") stay in the database for some time (default is two
+weeks) so you can reset back to it or create a new branch pointing to
+the original commit.
+
+For every move of a branch's head - with ``git commit``, ``git
+checkout``, ``git fetch``, ``git pull``, ``git rebase``, ``git reset``
+and so on - git stores a reference log (reflog for short). For every
+move git stores where the head was. Command ``git reflog`` can be used
+to view (and manipulate) the log.
+
+In addition to the moves of the head of every branch git stores the
+moves of the HEAD - a symbolic reference that (usually) names the
+current branch. HEAD is changed with ``git checkout $BRANCH``.
+
+By default ``git reflog`` shows the moves of the HEAD, i.e. the
+command is equivalent to ``git reflog HEAD``. To show the moves of the
+head of a branch use the command ``git reflog $BRANCH``.
+
+So to undo a ``git reset`` lookup the original commit in ``git
+reflog``, verify it with ``git show`` or ``git log`` and run ``git
+reset $COMMIT_ID``. Git stores the move of the branch's head in
+reflog, so you can undo that undo later again.
+
+In a more complex situation you'd want to move some commits along with
+resetting the head of the branch. Cherry-pick them to the new branch.
+For example, if you want to reset the branch ``master`` back to the
+original commit but preserve two commits created in the current branch
+do something like::
+
+ $ git branch save-master # create a new branch saving master
+ $ git reflog # find the original place of master
+ $ git reset $COMMIT_ID
+ $ git cherry-pick save-master~ save-master
+ $ git branch -D save-master # remove temporary branch
+
git revert: revert a commit
---------------------------
-How to undo a merge
-https://www.kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html
+``git revert`` reverts a commit or commits, that is, it creates a new
+commit or commits that revert(s) the effects of the given commits.
+It's the only way to undo published commits (``git commit --amend``,
+``git rebase`` and ``git reset`` change the branch in
+non-fast-forwardable ways so they should only be used for non-pushed
+commits.)
+
+There is a problem with reverting a merge commit. ``git revert`` can
+undo the code created by the merge commit but it cannot undo the fact
+of merge. See the discussion `How to revert a faulty merge
+<https://www.kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html>`_.
One thing that cannot be undone
-------------------------------
-"Commit early, commit often".
+Whatever you undo, there is one thing that cannot be undone -
+overwritten uncommitted changes. Uncommitted changes don't belong to
+git so git cannot help preserving them.
+
+Most of the time git warns you when you're going to execute a command
+that overwrites uncommitted changes. Git warns you when you try to
+switch branches with ``git checkout``. It warns you when you're going
+to rebase with non-clean working tree. It refuses to pull new commits
+over non-committed files.
+
+But there are commands that do exactly that - overwrite files in the
+working tree. Commands like ``git checkout $PATHs`` or ``git reset
+--hard`` silently overwrite files including your uncommitted changes.
+
+With that in mind you can understand the stance "commit early, commit
+often". Commit as often as possible. Commit on every save in your
+editor or IDE. You can edit your commits before pushing - change,
+reorder, combine, remove. But save your changes in git database,
+either commit changes or at least stash them with ``git stash``.
Merge or rebase?
For example::
$ git config branch.v1.rebase true
- $ git config branch.v2.rebase true
+ $ git config branch.master.rebase true
-After that ``git pull origin v2`` becomes equivalent to ``git pull
---rebase origin v2``.
+After that ``git pull origin master`` becomes equivalent to ``git pull
+--rebase origin master``.
In case when merge is preferred it is recommended to create new
commits in a separate feature or topic branch while using rebase to
$ git checkout -b issue-42 # create a new issue branch and switch to it
...edit/test/commit...
- $ git checkout v2
- $ git pull --rebase origin v2 # update v2 from the upstream
+ $ git checkout master
+ $ git pull --rebase origin master # update master from the upstream
$ git merge issue-42
$ git branch -d issue-42 # delete the topic branch
- $ git push origin v2
+ $ git push origin master
When the topic branch is deleted only the label is removed, commits
-are stayed in the database, they are now merged into v2::
+are stayed in the database, they are now merged into master::
- o--o--o--o--o--M--< v2 - the mainline branch
+ o--o--o--o--o--M--< master - the mainline branch
\ /
- --*--*--* - the topic branch, now unnamed
+ --*--*--* - the topic branch, now unnamed
The topic branch is deleted to avoid cluttering branch namespace with
small topic branches. Information on what issue was fixed or what
Git has a builtin merge strategy for what Python core developers call
"null-merge"::
- $ git merge -s ours v1 # null-merge v1 into v2
+ $ git merge -s ours v1 # null-merge v1 into master
-ReReRe
-======
+Advanced configuration
+======================
+
+Line endings
+------------
+
+Git has builtin mechanisms to handle line endings between platforms
+with different EOL styles. To allow git to do CRLF conversion assign
+``text`` attribute to files using `.gitattributes
+<https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html>`_.
+For files that have to have specific line ending assign ``eol``
+attribute. For binary files the attribute is, naturally, ``binary``.
+
+For example::
+
+ $ cat .gitattributes
+ *.py text
+ *.txt text
+ *.png binary
+ /readme.txt eol=CRLF
+
+To check what attributes git uses for files use ``git check-attr``
+command. For example::
-https://git-scm.com/book/en/Git-Tools-Rerere
+$ git check-attr -a -- \*.py
Advanced topics
Staging area
------------
-Staging area aka index is a distinguishing feature of git. See
-`WhatIsTheIndex
+Staging area aka index aka cache is a distinguishing feature of git.
+Staging area is where git collects patches before committing them.
+Separation between collecting patches and commit phases provides a
+very useful feature of git: you can review collected patches before
+commit and even edit them - remove some hunks, add new hunks and
+review again.
+
+To add files to the index use ``git add``. Collecting patches before
+committing means you need to do that for every change, not only to add
+new (untracked) files. To simplify committing in case you just want to
+commit everything without reviewing run ``git commit --all`` (or just
+``-a``) - the command adds every changed tracked file to the index and
+then commit. To commit a file or files regardless of patches collected
+in the index run ``git commit [--only|-o] -- $FILE...``.
+
+To add hunks of patches to the index use ``git add --patch`` (or just
+``-p``). To remove collected files from the index use ``git reset HEAD
+-- $FILE...`` To add/inspect/remove collected hunks use ``git add
+--interactive`` (``-i``).
+
+To see the diff between the index and the last commit (i.e., collected
+patches) use ``git diff --cached``. To see the diff between the
+working tree and the index (i.e., uncollected patches) use just ``git
+diff``. To see the diff between the working tree and the last commit
+(i.e., both collected and uncollected patches) run ``git diff HEAD``.
+
+See `WhatIsTheIndex
<https://git.wiki.kernel.org/index.php/WhatIsTheIndex>`_ and
`IndexCommandQuickref
<https://git.wiki.kernel.org/index.php/IndexCommandQuickref>`_ in Git
Wiki.
-Advanced configuration
-======================
+ReReRe
+======
-Line endings
-------------
+Rerere is a mechanism that helps to resolve repeated merge conflicts.
+The most frequent source of recurring merge conflicts are topic
+branches that are merged into mainline and then the merge commits are
+removed; that's often performed to test the topic branches and train
+rerere; merge commits are removed to have clean linear history and
+finish the topic branch with only one last merge commit.
-Git has builtin mechanisms to handle line endings.
+Rerere works by remembering the states of tree before and after a
+successful commit. That way rerere can automatically resolve conflicts
+if they appear in the same files.
-TODO: describe crlf configuration and .gitattributes.
+Rerere can be used manually with ``git rerere`` command but most often
+it's used automatically. Enable rerere with these commands in a
+working tree::
+ $ git config rerere.enabled true
+ $ git config rerere.autoupdate true
-Database maintenance
-====================
+You don't need to turn rerere on globally - you don't want rerere in
+bare repositories or repositories without branches; you only need
+rerere in repos where you often perform merges and resolve merge
+conflicts.
+
+See `Rerere <https://git-scm.com/book/en/Git-Tools-Rerere>`_ in The
+Book.
-TODO: dangling objects, git gc, git repack.
-https://gcc.gnu.org/ml/gcc/2007-12/msg00165.html
+Database maintenance
+====================
-http://vcscompare.blogspot.ru/2008/06/git-repack-parameters.html
+Git object database and other files/directories under ``.git`` require
+periodic maintenance and cleanup. For example, commit editing left
+unreferenced objects (dangling objects, in git terminology) and these
+objects should be pruned to avoid collecting cruft in the DB. The
+command ``git gc`` is used for maintenance. Git automatically runs
+``git gc --auto`` as a part of some commands to do quick maintenance.
+Users are recommended to run ``git gc --aggressive`` from time to
+time; ``git help gc`` recommends to run it every few hundred
+changesets; for more intensive projects it should be something like
+once a week and less frequently (biweekly or monthly) for lesser
+active projects.
+
+``git gc --aggressive`` not only removes dangling objects, it also
+repacks object database into indexed and better optimized pack(s); it
+also packs symbolic references (branches and tags). Another way to do
+it is to run ``git repack``.
+
+There is a well-known `message
+<https://gcc.gnu.org/ml/gcc/2007-12/msg00165.html>`_ from Linus
+Torvalds regarding "stupidity" of ``git gc --aggressive``. The message
+can safely be ignored now. It is old and outdated, ``git gc
+--aggressive`` became much better since that time.
+
+For those who still prefer ``git repack`` over ``git gc --aggressive``
+the recommended parameters are ``git repack -a -d -f --depth=20
+--window=250``. See `this detailed experiment
+<http://vcscompare.blogspot.ru/2008/06/git-repack-parameters.html>`_
+for explanation on the effects of these parameters.
+
+From time to time run ``git fsck [--strict]`` to verify integrity of
+the database. ``git fsck`` may produce a list of dangling objects;
+that's not an error, just a reminder to perform regular maintenance.
Tips and tricks
===============
-TODO: sticky options; example: git grep -O.
+Command-line options and arguments
+----------------------------------
+
+`git help cli
+<https://www.kernel.org/pub/software/scm/git/docs/gitcli.html>`_
+recommends not to combine short options/flags. Most of the times it
+works: ``git commit -av`` works perfectly, but there are situations
+when it doesn't. E.g., ``git log -p -5`` cannot be combined as ``git
+log -p5``.
+
+Some options have arguments, some even have default arguments. In that
+case the argument for such option must be spelled in a sticky way:
+``-Oarg``, never ``-O arg`` because for an option that has a default
+argument the latter means "use default value for option ``-O`` and
+pass ``arg`` further to the option parser". For example, ``git grep``
+has an option ``-O`` that passes found files to a program; default
+program for ``-O`` is pager (usually ``less``), but you can use your
+editor::
+
+ $ git grep -Ovim # but not -O vim
+
+BTW, there is a difference between running ``git grep -O`` and ``git
+grep -Oless`` - in the latter case ``git grep`` passes ``+/pattern``
+option to less.
-TODO: tricky options; example: git log -p3.
+bash/zsh completion
+-------------------
-TODO: bash/zsh completion, bash/zsh prompt.
-https://git.kernel.org/cgit/git/git.git/tree/contrib/completion
+It's a bit hard to type ``git rebase --interactive --preserve-merges
+HEAD~5`` manually even for those who are happy to use command-line,
+and this is where shell completion is of great help. Bash/zsh come
+with programmable completion, often automatically preinstalled and
+enabled, so if you have bash/zsh and git installed, chances are you
+are already done - just go and use it at the command-line.
+
+If you don't have necessary bits preinstalled, install and enable
+bash_completion package. If you want to upgrade your git completion to
+the latest and greatest download necessary file from `git contrib
+<https://git.kernel.org/cgit/git/git.git/tree/contrib/completion>`_.
+
+Git-for-windows comes with git-bash for which bash completion is
+installed and enabled.
+
+bash/zsh prompt
+---------------
+
+For command-line lovers shell prompt can carry a lot of useful
+information. To include git information in the prompt use
+`git-prompt.sh
+<https://git.kernel.org/cgit/git/git.git/tree/contrib/completion/git-prompt.sh>`_.
+Read the detailed instructions in the file.
+
+Search the Net for "git prompt" to find other prompt variants.
git on server
=============
-TODO: anonymous access; git over ssh; gitolite; gitweb; cgit; gitlab.
+The simplest way to publish a repository or a group of repositories is
+``git daemon``. The daemon provides anonymous access, by default it is
+read-only. The repositories are accessible by git protocol (git://
+URLs). Write access can be enabled but the protocol lacks any
+authentication means, so it should be enabled only within a trusted
+LAN. See ``git help daemon`` for details.
+
+Git over ssh provides authentication and repo-level authorisation as
+repositories can be made user- or group-writeable (see parameter
+``core.sharedRepository`` in ``git help config``). If that's too
+permissive or too restrictive for some project's needs there is a
+wrapper `gitolite <http://gitolite.com/gitolite/index.html>`_ that can
+be configured to allow access with great granularity; gitolite has a
+lot of documentation.
-http://gitolite.com/gitolite/index.html
+TODO: gitweb; cgit; Kallithea; pagure; gogs and gitea; gitlab.
https://git.kernel.org/cgit/git/git.git/tree/gitweb
http://git.zx2c4.com/cgit/
+https://kallithea-scm.org/
+
+https://pagure.io/
+
+http://gogs.io/ and http://gitea.io/
+
+https://about.gitlab.com/
+
+
From Mercurial to git
=====================
projects / git-wiki.git / blobdiff