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-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
+ $ 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 and
-updates remote-tracking branch.
+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-tracking 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 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
''''
``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.
+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.
====
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 contents of README file to the last but one
-commit in the current branch. By default a commit ID is simply HEAD;
+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
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/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
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