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I have not had a chance to read Oleg's PEP, but the devguide has the reverse docs at <a href="https://docs.python.org/devguide/gitdevs.html">https://docs.python.org/devguide/gitdevs.html</a> so we have the VCS docs down pat. :)
 <div class="gmail_quote"><div dir="ltr">On Sat, Sep 12, 2015, 06:59Â Oleg Broytman <<a href="mailto:phd@phdru.name">phd@phdru.name</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">PEP: XXX 
Title: Collecting information about git 
Version: $Revision$ 
Last-Modified: $Date$ 
Author: Oleg Broytman <<a href="mailto:phd@phdru.name" target="_blank">phd@phdru.name</a>> 
Status: Draft 
Type: Informational 
Content-Type: text/x-rst 
Created: 01-Jun-2015 
Post-History: 12-Sep-2015 
 
Abstract 
======== 
 
This Informational PEP collects information about git. There is, of 
course, a lot of documentation for git, so the PEP concentrates on 
more complex (and more related to Python development) issues, 
scenarios and examples. 
 
The plan is to extend the PEP in the future collecting information 
about equivalence of Mercurial and git scenarios to help migrating 
Python development from Mercurial to git. 
 
The author of the PEP doesn't currently plan to write a Process PEP on 
migration Python development from Mercurial to git. 
 
 
Documentation 
============= 
 
Git is accompanied with a lot of documentation, both online and 
offline. 
 
 
Documentation for starters 
-------------------------- 
 
Git Tutorial: `part 1 
<<a href="https://www.kernel.org/pub/software/scm/git/docs/gittutorial.html" rel="noreferrer" target="_blank">https://www.kernel.org/pub/software/scm/git/docs/gittutorial.html</a>>`_, 
`part 2 
<<a href="https://www.kernel.org/pub/software/scm/git/docs/gittutorial-2.html" rel="noreferrer" target="_blank">https://www.kernel.org/pub/software/scm/git/docs/gittutorial-2.html</a>>`_. 
 
`Git User's manual 
<<a href="https://www.kernel.org/pub/software/scm/git/docs/user-manual.html" rel="noreferrer" target="_blank">https://www.kernel.org/pub/software/scm/git/docs/user-manual.html</a>>`_. 
`Everyday GIT With 20 Commands Or So 
<<a href="https://www.kernel.org/pub/software/scm/git/docs/everyday.html" rel="noreferrer" target="_blank">https://www.kernel.org/pub/software/scm/git/docs/everyday.html</a>>`_. 
`Git workflows 
<<a href="https://www.kernel.org/pub/software/scm/git/docs/gitworkflows.html" rel="noreferrer" target="_blank">https://www.kernel.org/pub/software/scm/git/docs/gitworkflows.html</a>>`_. 
 
 
Advanced documentation 
---------------------- 
 
`Git Magic 
<<a href="http://www-cs-students.stanford.edu/~blynn/gitmagic/index.html" rel="noreferrer" target="_blank">http://www-cs-students.stanford.edu/~blynn/gitmagic/index.html</a>>`_, 
with a number of translations. 
 
`Pro Git <<a href="https://git-scm.com/book" rel="noreferrer" target="_blank">https://git-scm.com/book</a>>`_. The Book about git. Buy it at 
Amazon or download in PDF, mobi, or ePub form. It has translations to 
many different languages. Download Russian translation from `GArik 
<<a href="https://github.com/GArik/progit/wiki" rel="noreferrer" target="_blank">https://github.com/GArik/progit/wiki</a>>`_. 
 
`Git Wiki <<a href="https://git.wiki.kernel.org/index.php/Main_Page" rel="noreferrer" target="_blank">https://git.wiki.kernel.org/index.php/Main_Page</a>>`_. 
 
 
Offline documentation 
--------------------- 
 
Git has builtin help: run ``git help $TOPIC``. For example, run 
``git help git`` or ``git help help``. 
 
 
Quick start 
=========== 
 
Download and installation 
------------------------- 
 
Unix users: `download and install using your package manager 
<<a href="https://git-scm.com/download/linux" rel="noreferrer" target="_blank">https://git-scm.com/download/linux</a>>`_. 
 
Microsoft Windows: download `git-for-windows 
<<a href="https://github.com/git-for-windows/git/releases" rel="noreferrer" target="_blank">https://github.com/git-for-windows/git/releases</a>>`_ or `msysGit 
<<a href="https://github.com/msysgit/msysgit/releases" rel="noreferrer" target="_blank">https://github.com/msysgit/msysgit/releases</a>>`_. 
 
MacOS X: use git installed with `XCode 
<<a href="https://developer.apple.com/xcode/downloads/" rel="noreferrer" target="_blank">https://developer.apple.com/xcode/downloads/</a>>`_ or download from 
`MacPorts <<a href="https://www.macports.org/ports.php?by=name&substr=git" rel="noreferrer" target="_blank">https://www.macports.org/ports.php?by=name&substr=git</a>>`_ or 
`git-osx-installer 
<<a href="http://sourceforge.net/projects/git-osx-installer/files/" rel="noreferrer" target="_blank">http://sourceforge.net/projects/git-osx-installer/files/</a>>`_ or 
install git with `Homebrew <<a href="http://brew.sh/" rel="noreferrer" target="_blank">http://brew.sh/</a>>`_: ``brew install git``. 
 
`git-cola <<a href="https://git-cola.github.io/index.html" rel="noreferrer" target="_blank">https://git-cola.github.io/index.html</a>>`_ is a Git GUI 
written in Python and GPL licensed. Linux, Windows, MacOS X. 
 
`TortoiseGit <<a href="https://tortoisegit.org/" rel="noreferrer" target="_blank">https://tortoisegit.org/</a>>`_ is a Windows Shell Interface 
to Git based on TortoiseSVN; open source. 
 
 
Initial configuration 
--------------------- 
 
This simple code is often appears in documentation, but it is 
important so let repeat it here. Git stores author and committer 
names/emails in every commit, so configure your real name and 
preferred email:: 
 
Â Â $ git config --global <a href="http://user.name" rel="noreferrer" target="_blank">user.name</a> "User Name" 
Â Â $ git config --global user.email <a href="mailto:user.name@example.org" target="_blank">user.name@example.org</a> 
 
 
Examples in this PEP 
==================== 
 
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 ``master``. For most examples 
the currently checked out branch is ``master``. That is, it's assumed 
you have done something like that:: 
 
Â Â $ git clone <a href="https://git.python.org/python.git" rel="noreferrer" target="_blank">https://git.python.org/python.git</a> 
Â Â $ cd python 
Â Â $ git branch v1 origin/v1 
 
The first command clones remote repository into local 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. 
 
The same result can be achieved with commands:: 
 
Â Â $ git clone -b v1 <a href="https://git.python.org/python.git" rel="noreferrer" target="_blank">https://git.python.org/python.git</a> 
Â Â $ cd python 
Â Â $ git checkout --track origin/master 
 
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 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 
======================================= 
 
Remote-tracking branches are branches (pointers to commits) in your 
local repository. They are there for git (and 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``. 
 
To see the status of remote-tracking branches run:: 
 
Â Â $ git branch -rv 
 
To see local and remote-tracking branches (and tags) pointing to 
commits:: 
 
Â Â $ git log --decorate 
 
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:: 
 
Â Â $ git clone -b v1 <a href="https://git.python.org/python.git" rel="noreferrer" target="_blank">https://git.python.org/python.git</a> 
 
git clones remote repository ``<a href="https://git.python.org/python.git" rel="noreferrer" target="_blank">https://git.python.org/python.git``</a> to 
directory ``python``, creates a remote named ``origin``, 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-tracking branches 
------------------------------------------- 
 
There is a major difference between 
 
:: 
 
Â Â $ git fetch $REMOTE $BRANCH 
 
and 
 
:: 
 
Â Â $ git fetch $REMOTE $BRANCH:$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 (currently checked out branch, 
where HEAD is pointing to). 
 
The first command is used internally by ``git pull``. 
 
:: 
 
Â Â $ git pull $REMOTE $BRANCH 
 
is equivalent to 
 
:: 
 
Â Â $ git fetch $REMOTE $BRANCH 
Â Â $ git merge FETCH_HEAD 
 
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:: 
 
Â Â $ git fetch origin v1:v1Â # Update v1 
Â Â $ git pull --rebase origin masterÂ # Update the current branch master 
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â # using rebase instead of merge 
Â Â $ git merge v1 
 
If you have not yet pushed commits on ``v1``, though, the scenario has 
to become a bit more complex. Git refuses to update 
non-fast-forwardable branch, and you don't want to do force-pull 
because that would remove your non-pushed commits and you would need 
to recover. So you want to rebase ``v1`` but you cannot rebase 
non-current branch. Hence, checkout ``v1`` and rebase it before 
merging:: 
 
Â Â $ git checkout v1 
Â Â $ git pull --rebase origin v1 
Â Â $ git checkout master 
Â Â $ git pull --rebase origin master 
Â Â $ git merge v1 
 
It is possible to configure git to make it fetch/pull a few branches 
or all branches at once, so you can simply run 
 
:: 
 
Â Â $ git pull origin 
 
or even 
 
:: 
 
Â Â $ 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 
'''' 
 
Pushing is a bit simpler. There is only one command ``push``. When you 
run 
 
:: 
 
Â Â $ git push origin v1 master 
 
git pushes local v1 to remote v1 and local master to remote master. 
The same as:: 
 
Â Â $ 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. 
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 
editing and caveats`_ below. 
 
It is possible to configure git to make it push a few branches or all 
branches at once, so you can simply run 
 
:: 
 
Â Â $ git push origin 
 
or even 
 
:: 
 
Â Â $ 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 doesn't allow 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 repositories git prefers pull-based workflow. 
 
When you want to deploy code on a remote host and can only use push 
(because your workstation is behind a firewall and you cannot pull 
from it) you do that in two steps using two repositories: you push 
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 
<<a href="https://github.com/blog/1957-git-2-3-has-been-released#push-to-deploy" rel="noreferrer" target="_blank">https://github.com/blog/1957-git-2-3-has-been-released#push-to-deploy</a>>`_ 
for caveats; in 2.4 the push-to-deploy feature was `further improved 
<<a href="https://github.com/blog/1994-git-2-4-atomic-pushes-push-to-deploy-and-more#push-to-deploy-improvements" rel="noreferrer" target="_blank">https://github.com/blog/1994-git-2-4-atomic-pushes-push-to-deploy-and-more#push-to-deploy-improvements</a>>`_. 
 
 
Tags 
'''' 
 
Git automatically fetches tags that point to commits being fetched 
during fetch/pull. To fetch all tags (and commits they point to) run 
``git fetch --tags origin``. To fetch some specific tags fetch them 
explicitly:: 
 
Â Â $ git fetch origin tag $TAG1 tag $TAG2... 
 
For example:: 
 
Â Â $ git fetch origin tag 1.4.2 
Â Â $ git fetch origin v1:v1 tag 2.1.7 
 
Git doesn't automatically pushes tags. That allows you to have private 
tags. To push tags list them explicitly:: 
 
Â Â $ git push origin tag 1.4.2 
Â Â $ git push origin v1 master tag 2.1.7 
 
Or push all tags at once:: 
 
Â Â $ git push --tags origin 
 
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 and install the hooks 
manually. 
 
 
Commit editing and caveats 
========================== 
 
A warning not to edit published (pushed) commits also appears in 
documentation but it's repeated here anyway as it's very important. 
 
It is possible to recover from a forced push but it's PITA for the 
entire team. Please avoid it. 
 
To see what commits have not been published yet compare the head of the 
branch with its upstream remote-tracking branch:: 
 
Â Â $ git log origin/master..Â # from origin/master to HEAD (of master) 
Â Â $ git log origin/v1..v1Â # from origin/v1 to the head of v1 
 
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:: 
 
Â Â $ git log @{u}.. 
Â Â $ git log v1@{u}..v1 
 
To see the status of all branches:: 
 
Â Â $ git branch -avv 
 
To compare the status of local branches with a remote repo:: 
 
Â Â $ git remote show origin 
 
Read `how to recover from upstream rebase 
<<a href="https://git-scm.com/docs/git-rebase#_recovering_from_upstream_rebase" rel="noreferrer" target="_blank">https://git-scm.com/docs/git-rebase#_recovering_from_upstream_rebase</a>>`_. 
It is in ``git help rebase``. 
 
On the other hand don't be too afraid about commit editing. You can 
safely edit, reorder, remove, 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 have 
already been pushed. Not a problem until commits are in a public 
or shared repository. 
 
 
Undo 
==== 
 
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:: 
 
Â Â git checkout HEAD~ README 
 
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) 
commits. 
 
``git reset`` has three modes of operation - soft, hard and mixed. 
Default is mixed. ProGit `explains 
<<a href="https://git-scm.com/book/en/Git-Tools-Reset-Demystified" rel="noreferrer" target="_blank">https://git-scm.com/book/en/Git-Tools-Reset-Demystified</a>>`_ the 
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 from index changes added with ``git add`` for 
committing. See `The Book 
<<a href="https://git-scm.com/book/en/Git-Basics-Undoing-Things" rel="noreferrer" target="_blank">https://git-scm.com/book/en/Git-Basics-Undoing-Things</a>>`_ for details 
about unstaging and other undo tricks. 
 
 
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:: 
 
Â Â $ git branch save-master # create a new branch saving master 
Â Â $ git reflog # find the original place of master 
Â Â $ git reset $COMMIT_ID 
Â Â $ git cherry-pick save-master~ save-master 
Â Â $ 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 
<<a href="https://www.kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html" rel="noreferrer" target="_blank">https://www.kernel.org/pub/software/scm/git/docs/howto/revert-a-faulty-merge.html</a>>`_. 
 
 
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 doesn't allow you to switch 
branches with ``git checkout``. It stops 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 - edit commit 
messages, change commits, reorder, combine, split, remove. But save 
your changes in git database, either commit changes or at least stash 
them with ``git stash``. 
 
 
Merge or rebase? 
================ 
 
Internet is full of heated discussions on the topic: "merge or 
rebase?" Most of them are meaningless. When a DVCS is being used in a 
big team with a big and complex project with many branches there is 
simply no way to avoid merges. So the question's diminished to 
"whether to use rebase, and if yes - when to use rebase?" Considering 
that it is very much recommended not to rebase published commits the 
question's diminished even further: "whether to use rebase on 
non-pushed commits?" 
 
That small question is for the team to decide. The author of the PEP 
recommends to use rebase when pulling, i.e. always do ``git pull 
--rebase`` or even configure automatic setup of rebase for every new 
branch:: 
 
Â Â $ git config branch.autosetuprebase always 
 
and configure rebase for existing branches:: 
 
Â Â $ git config branch.$NAME.rebase true 
 
For example:: 
 
Â Â $ git config branch.v1.rebase true 
Â Â $ git config branch.master.rebase true 
 
After that ``git pull origin master`` becomes equivalent to ``git pull 
--rebase origin master``. 
 
It is recommended to create new commits in a separate feature or topic 
branch while using rebase to update the mainline branch. When the 
topic branch is ready merge it into mainline. To avoid a tedious task 
of resolving large number of conflicts at once you can merge the topic 
branch to the mainline from time to time and switch back to the topic 
branch to continue working on it. The entire workflow would be 
something like:: 
 
Â Â $ git checkout -b issue-42Â # create a new issue branch and switch to it 
Â Â Â Â ...edit/test/commit... 
Â Â $ git checkout master 
Â Â $ git pull --rebase origin masterÂ # update master from the upstream 
Â Â $ git merge issue-42 
Â Â $ git branch -d issue-42Â # delete the topic branch 
Â Â $ 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 master:: 
 
Â Â o--o--o--o--o--M--< master - the mainline branch 
Â Â Â Â \Â Â Â Â Â / 
Â Â Â Â Â --*--*--*Â Â Â Â Â Â Â - 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 
feature was implemented should be in the commit messages. 
 
 
Null-merges 
=========== 
 
Git has a builtin merge strategy for what Python core developers call 
"null-merge":: 
 
Â Â $ git merge -s ours v1Â # null-merge v1 into master 
 
 
Advanced configuration 
====================== 
 
Line endings 
------------ 
 
Git has builtin mechanisms to handle line endings between platforms 
with different end-of-line styles. To allow git to do CRLF conversion 
assign ``text`` attribute to files using `.gitattributes 
<<a href="https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html" rel="noreferrer" target="_blank">https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html</a>>`_. 
For files that have to have specific line endings assign ``eol`` 
attribute. For binary files the attribute is, naturally, ``binary``. 
 
For example:: 
 
Â Â $ cat .gitattributes 
Â Â *.py text 
Â Â *.txt text 
Â Â *.png binary 
Â Â /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 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 
<<a href="https://git.wiki.kernel.org/index.php/WhatIsTheIndex" rel="noreferrer" target="_blank">https://git.wiki.kernel.org/index.php/WhatIsTheIndex</a>>`_ and 
`IndexCommandQuickref 
<<a href="https://git.wiki.kernel.org/index.php/IndexCommandQuickref" rel="noreferrer" target="_blank">https://git.wiki.kernel.org/index.php/IndexCommandQuickref</a>>`_ in Git 
Wiki. 
 
 
ReReRe 
====== 
 
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. 
 
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. 
 
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:: 
 
Â Â $ git config rerere.enabled true 
Â Â $ git config rerere.autoupdate true 
 
You don't need to turn rerere on globally - you don't want rerere in 
bare repositories or single-branche repositories; you only need rerere 
in repos where you often perform merges and resolve merge conflicts. 
 
See `Rerere <<a href="https://git-scm.com/book/en/Git-Tools-Rerere" rel="noreferrer" target="_blank">https://git-scm.com/book/en/Git-Tools-Rerere</a>>`_ in The 
Book. 
 
 
Database maintenance 
==================== 
 
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 itÂ 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 
<<a href="https://gcc.gnu.org/ml/gcc/2007-12/msg00165.html" rel="noreferrer" target="_blank">https://gcc.gnu.org/ml/gcc/2007-12/msg00165.html</a>>`_ 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 
<<a href="http://vcscompare.blogspot.ru/2008/06/git-repack-parameters.html" rel="noreferrer" target="_blank">http://vcscompare.blogspot.ru/2008/06/git-repack-parameters.html</a>>`_ 
for explanation of 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 
=============== 
 
Command-line options and arguments 
---------------------------------- 
 
`git help cli 
<<a href="https://www.kernel.org/pub/software/scm/git/docs/gitcli.html" rel="noreferrer" target="_blank">https://www.kernel.org/pub/software/scm/git/docs/gitcli.html</a>>`_ 
recommends not to combine short options/flags. Most of the times 
combining 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 a list of names of the found files to 
a program; default program for ``-O`` is a pager (usually ``less``), 
but you can use your editor:: 
 
Â Â $ git grep -Ovim # but not -O vim 
 
BTW, if git is instructed to use ``less`` as the pager (i.e., if pager 
is not configured in git at all it uses ``less`` by default, or if it 
gets ``less`` from GIT_PAGER or PAGER environment variables, or if it 
was configured with ``git config --global core.pager less``, or 
``less`` is used in the command ``git grep -Oless``) ``git grep`` 
passes ``+/$pattern`` option to ``less`` which is quite convenient. 
Unfortunately, ``git grep`` doesn't pass the pattern if the pager is 
not exactly ``less``, even if it's ``less`` with parameters (something 
like ``git config --global core.pager less -FRSXgimq``); fortunately, 
``git grep -Oless`` always passes the pattern. 
 
 
bash/zsh 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 installed 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 installed, 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 
<<a href="https://git.kernel.org/cgit/git/git.git/tree/contrib/completion" rel="noreferrer" target="_blank">https://git.kernel.org/cgit/git/git.git/tree/contrib/completion</a>>`_. 
 
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 
<<a href="https://git.kernel.org/cgit/git/git.git/tree/contrib/completion/git-prompt.sh" rel="noreferrer" target="_blank">https://git.kernel.org/cgit/git/git.git/tree/contrib/completion/git-prompt.sh</a>>`_. 
Read the detailed instructions in the file. 
 
Search the Net for "git prompt" to find other prompt variants. 
 
 
git on server 
============= 
 
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 <<a href="http://gitolite.com/gitolite/index.html" rel="noreferrer" target="_blank">http://gitolite.com/gitolite/index.html</a>>`_ that can 
be configured to allow access with great granularity; gitolite is 
written in Perl and has a lot of documentation. 
 
Web interface to browse repositories can be created using `gitweb 
<<a href="https://git.kernel.org/cgit/git/git.git/tree/gitweb" rel="noreferrer" target="_blank">https://git.kernel.org/cgit/git/git.git/tree/gitweb</a>>`_ or `cgit 
<<a href="http://git.zx2c4.com/cgit/about/" rel="noreferrer" target="_blank">http://git.zx2c4.com/cgit/about/</a>>`_. Both are CGI scripts (written in 
Perl and C). In addition to web interface both provide read-only dumb 
http access for git (http(s):// URLs). 
 
There are also more advanced web-based development environments that 
include ability to manage users, groups and projects; private, 
group-accessible and public repositories; they often include issue 
trackers, wiki pages, pull requests and other tools for development 
and communication. Among these environments are `Kallithea 
<<a href="https://kallithea-scm.org/" rel="noreferrer" target="_blank">https://kallithea-scm.org/</a>>`_ and `pagure <<a href="https://pagure.io/" rel="noreferrer" target="_blank">https://pagure.io/</a>>`_, 
both are written in Python; pagure was written by Fedora developers 
and is being used to develop some Fedora projects. `Gogs 
<<a href="http://gogs.io/" rel="noreferrer" target="_blank">http://gogs.io/</a>>`_ is written in Go; there is a fork `Gitea 
<<a href="http://gitea.io/" rel="noreferrer" target="_blank">http://gitea.io/</a>>`_. 
 
And last but not least, `Gitlab <<a href="https://about.gitlab.com/" rel="noreferrer" target="_blank">https://about.gitlab.com/</a>>`_. It's 
perhaps the most advanced web-based development environment for git. 
Written in Ruby, community edition is free and open source (MIT 
license). 
 
 
>From Mercurial to git 
===================== 
 
There are many tools to convert Mercurial repositories to git. The 
most famous are, probably, `hg-git <<a href="https://hg-git.github.io/" rel="noreferrer" target="_blank">https://hg-git.github.io/</a>>`_ and 
`fast-export <<a href="http://repo.or.cz/w/fast-export.git" rel="noreferrer" target="_blank">http://repo.or.cz/w/fast-export.git</a>>`_ (many years ago 
it was known under the name ``hg2git``). 
 
But a better tool, perhaps the best, is `git-remote-hg 
<<a href="https://github.com/felipec/git-remote-hg" rel="noreferrer" target="_blank">https://github.com/felipec/git-remote-hg</a>>`_. It provides transparent 
bidirectional (pull and push) access to Mercurial repositories from 
git. Its author wrote a `comparison of alternatives 
<<a href="https://github.com/felipec/git/wiki/Comparison-of-git-remote-hg-alternatives" rel="noreferrer" target="_blank">https://github.com/felipec/git/wiki/Comparison-of-git-remote-hg-alternatives</a>>`_ 
that seems to be mostly objective. 
 
To use git-remote-hg, install or clone it, add to your PATH (or copy 
script ``git-remote-hg`` to a directory that's already in PATH) and 
prepend ``hg::`` to Mercurial URLs. For example:: 
 
Â Â $ git clone <a href="https://github.com/felipec/git-remote-hg.git" rel="noreferrer" target="_blank">https://github.com/felipec/git-remote-hg.git</a> 
Â Â $ PATH=$PATH:"`pwd`"/git-remote-hg 
Â Â $ git clone hg::<a href="https://hg.python.org/peps/" rel="noreferrer" target="_blank">https://hg.python.org/peps/</a> PEPs 
 
To work with the repository just use regular git commands including 
``git fetch/pull/push``. 
 
To start converting your Mercurial habits to git see the page 
`Mercurial for Git users 
<<a href="https://mercurial.selenic.com/wiki/GitConcepts" rel="noreferrer" target="_blank">https://mercurial.selenic.com/wiki/GitConcepts</a>>`_ at Mercurial wiki. 
At the second half of the page there is a table that lists 
corresponding Mercurial and git commands. Should work perfectly in 
both directions. 
 
 
Copyright 
========= 
 
This document has been placed in the public domain. 
 
 
 
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