Offline documentation
---------------------
-Git has builtin help: run ``git help TOPIC``. For example, run
+Git has builtin help: run ``git help $TOPIC``. For example, run
``git help git`` or ``git help help``.
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 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 branch.
+remotes/origin/v1 as its upstream remote-tracking branch.
The same result can be achieved with commands::
$ 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 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
Git terminology can be a bit misleading. Take, for example, the term
"branch". In git it has two meanings. A branch is a directed line of
commits (possibly with merges). And a branch is a label or a pointer
-assigned to a line of commits. It is important to differentiate when
-you talk about commits and when about their labels. Lines of commits
-are by itself unnamed and are usually only lengthening and merging.
+assigned to a line of commits. It is important to distinguish when you
+talk about commits and when about their labels. Lines of commits are
+by itself unnamed and are usually only lengthening and merging.
Labels, on the other hand, can be created, moved, renamed and deleted
freely.
Remote repositories and remote branches
=======================================
-Another example of slightly misleading terminology. Remote
-repositories are really remote, you access them via network (well, a
-remote repository can be on your local disk, but it's still remote
-because it's not the current repo).
+Remote-tracking branches are branches (pointers to commits) in your
+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/master``.
-Remote branches, on the other hand, are branches (pointers to commits)
-in your 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 branches
-live under ``remotes/REMOTE`` namespaces, e.g. ``remotes/origin/v2``.
-
-To see the status of remote branches run::
+To see the status of remote-tracking branches run::
$ git branch -rv
-To see local and remote branches (and tags) pointing to commits::
+To see local and remote-tracking branches (and tags) pointing to
+commits::
$ git log --decorate
-You never do your own development on remote branches. You create a
-local branch that has a remote branch as upstream and do development
-on that local branch. On push git pushes commits to the remote repo
-and updates remote branches, on pull git fetches commits from the
-remote repo, updates remote branches and fast-forwards, merges or
-rebases local branches.
+You never do your own development on remote-tracking branches. You
+create a local branch that has a remote branch as upstream and do
+development on that local branch. On push git pushes commits to the
+remote repo and updates remote-tracking branches, on pull git fetches
+commits from the remote repo, updates remote-tracking branches and
+fast-forwards, merges or rebases local branches.
When you do an initial clone like this::
$ git clone -b v1 http://git.python.org/python.git
git clones remote repository ``http://git.python.org/python.git`` to
-directory ``python``, creates remote branches, creates a local branch
-``v1``, configure it to track upstream remotes/origin/v1 branch and
-checks out ``v1`` into the working directory.
+directory ``python``, creates remote-tracking branches, creates a
+local branch ``v1``, configure it to track upstream remotes/origin/v1
+branch and checks out ``v1`` into the working directory.
-Updating local and remote branches
-----------------------------------
+Updating local and remote-tracking branches
+-------------------------------------------
There is a major difference between
::
- $ git fetch REMOTE BRANCH
+ $ git fetch $REMOTE $BRANCH
and
::
- $ git fetch REMOTE BRANCH:BRANCH
+ $ 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. But it doesn't
-update any branch (doesn't move any pointer).
+The first command fetches commits from the named $BRANCH in the
+$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 the local
-branch BRANCH and its upstream remote branch. But it refuses to update
-branches in case of non-fast-forward. And it refuses to update the
-current branch.
+The second command fetches commits from the named $BRANCH in the
+$REMOTE repository that are not in your repository and updates both
+the local branch $BRANCH and its upstream remote-tracking branch. But
+it refuses to update branches in case of non-fast-forward. And it
+refuses to update the current branch.
The first command is used internally by ``git pull``.
::
- $ git pull REMOTE BRANCH
+ $ git pull $REMOTE $BRANCH
is equivalent to
::
- $ git fetch REMOTE BRANCH
- $ git merge FETCH_HEAD # FETCH_HEAD is a literal here
+ $ git fetch $REMOTE $BRANCH
+ $ git merge FETCH_HEAD
-Certainly, BRANCH in that case should be your current branch. If you
+Certainly, $BRANCH in that case should be your current branch. If you
want to merge a different branch into your current branch first update
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 pull
+Default remote repository for fetching/pulling is origin. Default set
+of references to fetch is calculated using matching algorithm: git
+fetches all branches having the same name on both ends.
+
Push
''''
::
- $ git push origin v1 v2
-
-git guesses (knowing upstream remote branches) that you really want
+ $ git push origin v1 master
-::
+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 branches. Git
-refuses to push commits that aren't fast-forwardable. You can
-force-push anyway, but please remember - you can force-push to your
-own repositories but don't force-push to public or shared repos. If
-you find git refuses to push commits that aren't fast-forwardable,
+Git pushes commits to the remote repo and updates remote-tracking
+branches. Git refuses to push commits that aren't fast-forwardable.
+You can force-push anyway, but please remember - you can force-push to
+your own repositories but don't force-push to public or shared repos.
+If you find git refuses to push commits that aren't fast-forwardable,
better fetch and merge commits from the remote repo (or rebase your
commits on top of the fetched commits), then push. Only force-push if
you know what you do and why you do it. See the section `Commit
$ git push
+Default remote repository for pushing is origin. Default set
+of references to push in git before 2.0 is calculated using matching
+algorithm: git pushes all branches having the same name on both ends.
+Default set of references to push in git 2.0+ is calculated using
+simple algorithm: git pushes the current branch back to its
+@{upstream}.
+
+To configure git before 2.0 to the new behaviour run::
+
+$ git config push.default simple
+
+To configure git 2.0+ to the old behaviour run::
+
+$ git config push.default matching
+
Git refuses to push a branch if it's the current branch in the remote
non-bare repository: git refuses to update remote working directory.
You really should push only to bare repositories. For non-bare
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
''''
``git fetch --tags origin``. To fetch some specific tags fetch them
explicitly::
- $ git fetch origin tag TAG1 tag TAG2...
+ $ git fetch origin tag $TAG1 tag $TAG2...
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.
-Don't move tags with ``git tag -f`` 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
entire team. Please avoid it.
To see what commits have not been published yet compare the head of the
-branch with its upstream remote branch::
+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 branch git maintains an
-alias @{upstream} (short version @{u}), so the commands above can be
-given as::
+For every branch that has an upstream remote-tracking branch git
+maintains an alias @{upstream} (short version @{u}), so the commands
+above can be given as::
$ git log @{u}..
$ git log v1@{u}..v1
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.
====
Whatever you do, don't panic. Almost anything in git can be undone.
+
+git checkout: restore file's content
+------------------------------------
+
``git checkout``, for example, can be used to restore the content of
file(s) to that one of a commit. Like this::
git checkout HEAD~ README
-The commands restores the contente of README file to the last but one
-commit in the current branch. By default a commit ID is simple HEAD;
+The commands restores the contents of README file to the last but one
+commit in the current branch. By default the commit ID is simply HEAD;
i.e. ``git checkout README`` restores README to the latest commit.
(Do not use ``git checkout`` to view a content of a file in a commit,
use ``git cat-file -p``; e.g. ``git cat-file -p HEAD~:path/to/README``).
+git reset: remove (non-pushed) commits
+--------------------------------------
+
``git reset`` moves the head of the current branch. The head can be
moved to point to any commit but it's often used to remove a commit or
a few (preferably, non-pushed ones) from the top of the branch - that
-is, to move the branch backward in order to undo a few non-pushed
+is, to move the branch backward in order to undo a few (non-pushed)
commits.
``git reset`` has three modes of operation - soft, hard and mixed.
difference very clearly. Bare repositories don't have indices or
working trees so in a bare repo only soft reset is possible.
+Unstaging
+'''''''''
+
Mixed mode reset with a path or paths can be used to unstage changes -
-that is, to remove changes added with ``git add`` for committing. See
-`The Book <https://git-scm.com/book/en/v2/Git-Basics-Undoing-Things>`_
-for details about unstaging and other undo tricks.
+that is, to remove from index changes added with ``git add`` for
+committing. See `The Book
+<https://git-scm.com/book/en/Git-Basics-Undoing-Things>`_ for details
+about unstaging and other undo tricks.
-TODO: describe undo strategies: git reflog, git revert.
-"Commit early, commit often".
+git reflog: reference log
+-------------------------
-How to undo a merge
-https://www.kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html
+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
+---------------------------
+
+``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
+-------------------------------
+
+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?
and configure rebase for existing branches::
- $ git config branch.NAME.rebase true
+ $ git config branch.$NAME.rebase true
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
+======================
-https://git-scm.com/book/en/Git-Tools-Rerere
+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::
+
+$ 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: one 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 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) use ``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
-======================
-
-Line endings
-------------
-
-Git has builtin mechanisms to handle line endings.
+ReReRe
+======
-TODO: describe crlf configuration and .gitattributes.
+https://git-scm.com/book/en/Git-Tools-Rerere
Database maintenance
====================
TODO: dangling objects, git gc, git repack.
+
https://gcc.gnu.org/ml/gcc/2007-12/msg00165.html
+http://vcscompare.blogspot.ru/2008/06/git-repack-parameters.html
+
Tips and tricks
===============
projects / git-wiki.git / blobdiff