path: root/using-git.texinfo

\input texinfo   @c -*-texinfo-*-

@c %**start of header
@setfilename using-git.info
@settitle using git
@afourpaper
@documentencoding UTF-8
@documentlanguage en
@finalout
@c %**end of header



@dircategory Version Control
@direntry
* using git: (using git).             Using the Git source control management
@end direntry


@copying
Copyright @copyright{} 2013 Mattias Andrée

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
``GNU Free Documentation License''.
@end quotation
@end copying

@ifnottex
@node Top
@top Using Git
@insertcopying
@end ifnottex

@titlepage
@title Using Git
@author by Mattias Andrée (maandree)

@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents



@menu
* Getting started::
* Introduction::
* Branching out::
* Collaborating::
* Basic commands::
* I just don't know what went wrong::
* Version control::
* Interface::
* Beyond Git::
* GNU Free Documentation License::
* Glossary::
@end menu



@node Getting started
@chapter Getting started

@menu
* Identify yourself::
* Create a repository::
* Create an origin::
* Gratis hosting::
* Generate your key::
@end menu



@node Identify yourself
@section Identify yourself

The first thing you want to do right off the bat
is to identify yourself: add your name and e-mail
address to your Git configurations. This is
done with two simple commands:

@example
git config --global user.name 'YOUR NAME'
git config --global user.email 'YOUR_EMAIL_ADDRESS'
@end example

It is possible to sign your work with GPG. If you
are planning on doing this, and doing this with
another GPG key then your default key, you can
configure Git to using another key by default:

@example
git configre --global user.signingkey YOUR_GPG_KEY_ID
@end example



@node Create a repository
@section Create a repository

A repository is a directory under source control,
normally your project you are working on.

Create an empty directory and @command{cd} into it:

@example
mkdir MY_PROJECT
cd MY_PROJECT
@end example

When you are inside the directory for the repository
issus the git command to initialise the repository:

@example
git init
@end example

This command creates a directory namend @file{.git}
inside the directory with all data git requires to
operate on the repository.

The next thing you want to do is to create a
@file{.gitignore} file, it is used to keep track
of with files that should be be included in the
repository, unless overruled with a forced staging.

A good base @file{.gitignore} content you probably
always want to use is:

@example
_/
# It is a good idea to allow the directory _ to
# contain temporary file you do not want to stage.

.*
# Generally you probably do not want to include
# hidden files.

!.git*
# But you do generally want to include files
starting with .git, such as .gitignore.

\#*\#
*~
*.bak
# And you do not want to include backup files.
@end example

Git parses @file{.gitignore} with wildcards,
@code{#} for comments and @code{!} for inclusion
rather than exclusion, latter entires override
earlier entries.

When you have created your @file{.gitignore} you
are ready to stage it and make your first commit:

@example
git add .gitignore
git commit -m 'first commit'
@end example



@node Create an origin
@section Create an origin

It is a good idea to create a backup repostory,
so you do not lose your work on a disc failure,
filesystem corruption or accidental removal.

You can such repostory for allowing collaboration
with a command repository that the collaborators
can all submit and fetch commits from.

This repository is customarly called `origin'.
And it is a bare repository, meaning that it
only hold the data in the @file{.git} directory
and cannot be used as the working directory.

@example
mkcd -p /srv/git/MY_REPOSITORY.git
cd /srv/git/MY_REPOSITORY.git
git init --bare

cd -  # Go back to your project respository
git remote add origin file:///srv/git/MY_REPOSITORY.git
git push -u orgin master  # master is the bransh you are working in
@end example

It is standard to append @file{.git} to the
end of the repository name when it is bare.

To submit your changes to origin you can now
use the command @command{git push}. To fetch
updates others have made, use the command
@command{git pull}.



@node Gratis hosting
@section Gratis hosting

As seen you do not need host, but it is a grate
way for making your projects available to the world.

Here is a lost of gratis git hosting services that
hosts Free Software.

@table @asis
@item @bullet{} @url{https://savannah.nongnu.org/, Savannah}
Hosts Free Software only, and projects are audited
for licensing issues upon registration. So it can
take a short time before it is accepted, but you your
project will not use non-Free Software and no license
information will be missing. Savannah runs on only
Free Software.

@item @bullet{} @url{https://gna.org, Gna!}
For Free Software projects only. Gna! runs on only
Free Software.

@item @bullet{} @url{https://bitbucket.org, BitBucket}
Gratis for 5 users, with unlimied number of private
repositories for 5 collaborators.

@item @bullet{} @url{https://github.com/, GitHub}
5 private repositories for students, for two yours
and reactivatable when expired. Teachers and student
organisations can get private repositories, as many
as required, for an organisation.

@item @bullet{} @url{https://www.assembla.com/catalog/51-free-private-git-repository-package?type=private&ad=git-wiki, Assembla}
Hosting limited to 2 GB with one free private
repository for three users.

@item @bullet{} @url{https://www.cloudforge.com/pricing, CloudForge}
Hosting limited to 2 GB.

@end table

You should note that there are, other, git hosting
services that does not allow Free Software. Some
of them will allow Open Source, some will allow
Free Software, but not gratis.



@node Generate your key
@section Generate your key

Many Git servers authenticate using public
SSH keys. If you do not already have SSH
installed, install it, it is probably named
@code{openssh} in your GNU/Linux distributions'
package repository.

Before create an SSH key, check if you already
have one. You are looking for a pair of
@file{id_rsa.pub} and @file{id_rsa}, in
@file{~/.ssh}. @file{id_rsa} is your private
key and should not be shared or made public.
@file{id_rsa.pub} is you public key and is
the file you want to upload you your Git
hosting server.

If you do not already have a key, you can
create it with:

@example
ssh-keygen -t rsa -C 'YOUR_EMAIL_ADDRESS'
@end example



@node Introduction
@chapter Introduction

@menu
* What is Git?::
* It is distributed::
* Integrity::
* Online documentation::
@end menu



@node What is Git?
@section What is Git?

Git is a version control system known for
its lightning speed@footnote{Specially
under POSIX compatible systems} and being
distributed. A version control system is a
system for storing changes in a history
tree and allow for multiple people to work
on the same project without the risk of the
code being too new to accept a submitted patch.

When you are working it is important to keep
track of changes so that you can find when
edit step broke the system. But version
control also lets you create branches, these
are different versions of the same project
being developed concurrently which lets your
team implement features in parallel and
merge them in into the mainline when stable.

And other important feature of version
control that can be used to tag releases
of the code. If you have release a program
and is sent a bug report you may want to
test it one both the current version and
the version the user used.



@node It is distributed
@section It is distributed

Traditionally, version control systems
were centralised. Every project has one
repository all contributers pushed and
pulled from. Git is distributed, this
means that contributers clone the
respositor and words on that clone
instead of ``checking out'' the current
tip of the source code. This actually
means that there are multiple backups
of the respository is recovering a
crash or corruption will be a breeze.

It is a popular misconception that
distributed systems are not suited for
projects that requires an official
central repository. This is far from
true; projects have a central blessed
repository, possibly with mirrors.

A blessed repository, refered to as
the upstream, is the projects official
respository. Its maintained by a select
few with input from submitted updates.
But the upstream can also be a shared
repository, this is the classical
Subversion-style workflow, where everyone
pulls from and pushes to. Git does not
allow you to push before you have pulled
to latest commit so this workflow works
fine.

Small projects will usally have one
maintainer and contributors clones her
blessed repository and sends submissons
to her. Larger projects may have multiple
maintainers that helps with excepting
submissons. A common model like this,
that you often se on GitHub, is the
integeration manager workflow, where the
maintainer is an integeration manager
than excepts pull requests from developers
that have public repositores, often
called forks (which should not be confused
with a project fork where the forker
is taked the project in another direction
is does not requests pulls.)

Even larger project will usablly work
with a dictator and lieutenants workflow
where developers clones the blessed
repository and submits patches to the
lieutenants who in turn submits the the
dictator that finally pushes the changes
to the blessed repository.



@node Integrity
@section Integrity

Git cryptographically hashes all data
associated with a commit, including the
prior commit. This makes it unfeasible
to modify a commit without changing the
commit ID; change the commit ID brakes
the commit history and would therefore
get noticed as the develops cannot work
against a broken commit history.

Additionally commits can be signed with
GPG, so you can be sure that the commit
is how is says he is.



@node Online documentation
@section Online documentation

As with most software packages, Git
includes online documentation, accessible
in several ways. The simplest way, this
will working on all systems is by add
@option{--help} to the command @command{git}
or @command{git VERB}.

Git is a project started by Linus Torvalds,
the creator of the Linux kernel, so naturally
it has manpages, but not any official
@command{info} manual. Since @command{info}
supports manpage you can use @command{info}
in place of @command{man}.

Git includes several manpages, one manpage
for every Git command: @command{man git VERB}
or alternatively @command{man git-VERB}, and
manpages on special topic:

@itemize
@item @command{man git}
@item @command{man gitattributes}
@item @command{man gitcli}
@item @command{man gitcore-tutorial}
@item @command{man gitcredentials}
@item @command{man gitdiffcore}
@item @command{man gitglossary}
@item @command{man githooks}
@item @command{man gitignore}
@item @command{man gitmodules}
@item @command{man gitnamespaces}
@item @command{man gitrepository-layout}
@item @command{man gittutorial}
@item @command{man gittutorial-2}
@item @command{man gitworkflows}
@end itemize



@node Branching out
@chapter Branching out

@menu
* Workflow::
* Creating branches::
* Merging branches::
@end menu



@node Workflow
@section Workflow

Git encourage you to create multiple local
branches of your repository. A branch is a
fork of your commit history, it allows you
to implement features in parallel. The most
important part with this is that you can
fix bugs meanwhile you are working one big
new features.

You main branch is by default called `master',
from it, it is recommended to have a branch
called `develop'. The develop branch is the
branch you work on, and when it is stable,
you merge it with the master branch.

From the develop branch you can branch out
an create topic branches, an disposable
experiments.



@node Creating branches
@section Creating branches

The quickest way to create a new branch and
start working on it is to issue a checkout
command that create a new branch:

@example
git checkout -b BRANCH_NAME
@end example

After issuing this command you are located
in a new branch. The create it in the origin,
make a push:

@example
git push -u origin BRANCH_NAME
@end example

From this point on you can push without
parameters:

@example
git push
@end example

The @option{-u origin BRANCH_NAME} is just
to initially tell which remote repository
a pushes should go to.

To switch branch use the checkout command:

@example
git checkout BRANCH_NAME
@end example



@node Merging branches
@section Merging branches

The merge a branch into another, switch
to one of them and pull the other:

@example
git checkout MERGER
git pull . MERGEE
@end example

In the default mode, @command{git pull . MERGEE}
is a short and fore a fetch and merge:

@example
git fetch MERGEE &&
git merge MERGEE
@end example

If you two cannot be automatically merged,
you will you get a merge conflict. A case
where you will get merge conflicts is when
one of the branches as made a modification
where the other has change the indention,
so keep to a coding style from the start;
or both has edited the same lines.

If you get a merge conflict, git will tell
you so, in which files there are conflicts,
and exit with the return code 1 to indicated
that the merge was not successful and human
intervention is required. If the merger
branch as a file with the line
@code{Hello world} and the mergee branch
as the line @code{hello world!}, the
file will contain:

@example
<<<<<<< HEAD
Hello world
=======
hello world!
>>>>>>> xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
@end example

Where
@code{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
is the lower case hexadecimnal represention of
the commit ID at the tip of the mergee branch,
which is a SHA-1 hash sum of the commit.

After a merge conflict you will need to stage
the files and make a new commit.



@node Collaborating
@chapter Collaborating

@menu
* Cloning a repository::
* Submitting patches::
* Accepting patches::
* Making pull requests::
@end menu



@node Cloning a repository
@section Cloning a repository

The first thing you need to do in order
to begin collaboration is the clone the
repository:

@example
git clone REPOSITORY -o upstream
@end example

By including @option{-o upstream}, git
sets up the cloned repository as a
remote repository named `upstream'.

If you want to access a branch in the
upstream repository, use
@code{upstream/BRANCH} as the branch name.



@node Submitting patches
@section Submitting patches

The best way to create a patch is with Git's
@command{format-patch} command. Assuming
you began from @code{upstream/master}:

@example
git format-patch upstream/master
@end example

This command with create a patch whose name
will be printed by @command{git format-patch}.

Creating a patch this way will keep track
of the commit messages, and the individual
commits. Another advantage with it is that
it can easily be submitted to a mailing list,
which the common way for large projects for
accepting patches.

The created patch file is formated as an
e-mail, with `[PATCH]' in the beginning of
the subject line. If you update the patch
it is customary to use `[PATCH v2]' instread
and `[PATCH v3]' on the second update.
If the patch, however it not readly for
being included, but is rather for discussion,
use `PATCH/RFC'@footnote{RFC is an abbreviation
for `Request for comments'} instead of `PATCH'.

To send the patch, use @command{git send-email}:

@example
git send-email --to=EMAIL_ADDRESS_TO_SEND_TO PATCH_FILE
@end example

If you have registered to the mailing list,
or for some other reason, want to send under
a different e-mail address then you made the
commits with, you need to specify an envelop
send, by adding an option:

@example
--envelope-sender=SENDER_EMAIL_ADDRESS
@end example

You will also need the specify which SMTP
server to use, authorisation and configurations:

@example
--smtp-server=DOMAIN    # it usally is prefixed with smtp.
--smtp-server-port=PORT
--smtp-encryption=ssl   # or tls
--smtp-user=ACCOUNT     # usally just the username without domain
--smtp-pass=PASSPHRASE
@end example

If you are using a forwarding e-mail, such
as @@member.fsf.org, you send from using your
normal e-mail, but use the forwarding e-mail
address as the envelop-sender, most e-mail
server should accept this.

If you are replying to a message in the mailing
list, perhaps with an updated patch, you should
specify the message ID of the message to replay
to. This done my adding the option:

@example
--in-reply-to=MESSAGE_ID
@end example

To get the message ID, open the message in your
e-mail client and choose to see all headers ---
if not possible: download the it as an mbox file
and open it in an text editor --- a look for:

@example
Message-ID: <MESSAGE_ID>
@end example

As indicated here, it is surrended by less than
and grater than-signs. You should, if you have
subscribed to the mailing list, have gotten it
send to your e-mail. If you do not have it, go
the the mailing lit and click that you want to
reply, it will open your e-mail client in compose
mode and the in-reply-to address will have been
set to the proper message ID.



@node Accepting patches
@section Accepting patches

To apply a patch, use the @command{git am}
@footnote{`am' stands for `apply mailbox',
but it works on regular patch files}
command:

@example
git am PATCH_FILE
@end example

Is good practice to sign off commits to
help establish a chain to trace submissions,
and some projects will require it. To
sign off with @command{git am}, just add
@command{--signoff}.



@node Making pull requests
@section Making pull requests

A less feature rich alternative than
patches are pull request, but they are
easier to just because you do know need
to know anything to make a pull request
and to accept them you just need to
know how to pull from other repositories.

Git does however provide a command
the produces a clean standard message
than can be posted on a mailing list.
To do this just type:

@example
git request-pull FORKING_POINT_COMMIT YOUR_URL
@end example

Additionally you can add a commit that
the pull requests stops at, if you have
another commit than @code{HEAD} --- the
current commit you are working at --- in
mind. You can also add @option{-p} if
you want to see the changes.



@node Basic commands
@chapter Basic commands

@menu
* The trees of Git::
* File operations::
* Go back in time::
@end menu



@node The trees of Git
@section The trees of Git

Git has four trees should know about
to better understand how Git works.

The first tree you encounter is the
working directory. The tree begins
in the parent so called git directory;
the directory you executed
@command{git init} in, and contains
the directory @file{.git}.

When you are using @command{git add}
to stage files you encounter the next
tree. This tree is called the index,
and is separate from the working
directory, when you stage a file,
you stage an edit, if you edit the
file further those changes does not
make it into the index until you
restage the file.

When you have done some work ---
just a small logical step is recommended
--- and want to save your changes you
commit then with @command{git commit}.
This is when you encounter the third
tree, the @code{HEAD}. @code{HEAD} is
the file tree of the last commit, and
it is updated when make a commit.

The fourth tree is not a file tree,
it is the commit tree. The important
thing with Git is that this tree is
not linear, it is a directed acyclic
graph, so it is not really a tree,
but you can think of it as one because
you are normally only interested
in the leaves, your branches.



@node File operations
@section File operations

Their are four basic options you can
do on files: add, update, remove and
rename, adding and update is done
with the same command:

@example
git add FILE
@end example

To remove a file or rename a file,
just do as you normally would without
git, but prepand @code{git}:

@example
git rm FILE           # Remove FILE
git mv FILE NEW_NAME  # Rename FILE to NEW_NAME
@end example

If an directory in becomes empty
in the working directory it is
automatically removed from working
directory. And directories are never
tracked by Git, so you cannot have
an empty directory in a commit.

You can also use @command{git add -u}
@footnote{@option{-u} is the short
option for @option{--update}.} to
stage an edit in an already tracked
file or stage the removal of it
if it as been removed from the
working directory.

A caveat with @command{git mv} is
that is that is that same thing as
typing:

@example
cp FILE NEW_NAME
git rm FILE
git add NEW_NAME
@end example

In other words, the history for
the file is reset and if you do
this at the same time someone
edits the file you will get a
merge conflict.

This is not a problem with GNU
Arch because it keeps track of
which file is which by giving
it an unique identifier, and you
may think that would have been
a good think. But if the content
of the file depends on the file's
name, or the other way around,
and a line with such dependency
is added, the file's content
would become bad. Well it is
debatable since the case could
be that another file depends on
the renamed files name, and
someone could make a change in
that file. But fixing a merge
conflict when you have only
renamed the file is not too hard
and it eliminates a potatial
maintenance miss.

If you want do know the file
staging difference between the
index and working directory
type @command{git status}.



@node Go back in time
@section Go back in time

Because git keeps track of what
has changed it has a log you
access, which has commit messages,
so you know when something has
happend or what has happen lately.
To read the log type:

@example
git log
@end example

If you want to know which files
have changes, you can use
@command{git whatchanged} instead.

If you want to take a closer look
a commit an see the state of the
project at the commit type:

@example
git stash               # Only if you have uncommited changes, this
                        # saves you changes outside the tree in a stack.
git checkout COMMIT_ID  # Take a look around!
git checkout -          # Checking out - means that you checkout the
                        # commit you were on before the last checkout.
                        # Kind of like `cd -'.
git stash pop           # Only if you have uncommited changes, this
                        # reapplies the changes you saved with `git stash'
                        # and removes it from that stack.
@end example

If you instead what to see all
changes from that point of time type:

@example
git diff COMMIT_ID
@end example

Or for a specific file:

@example
git diff COMMIT_ID FILE
@end example

If you decide that you want to go back
permanently to this state you type:

@example
git revert THE_COMMIT_ID_OF_THE_COMMIT_AFTER_THAT_COMMIT..HEAD
@end example

If you have not push the commits you
want to revert you can do a reset instead,
thay way the are irreverable removed
instead of a new commit being made:

@example
git reset --hard COMMIT_ID
@end example

But you should think of that as running
as root:

@cartouche
@noindent
Chris: root is the number zero user,
it is main user in your system, it
can do everything, it can literally
delete the filesystem while your
operating system is running.

@noindent
Bryan: Yeah, it is a grate user in
that regard.

@noindent
Chris: Yeah. Yeah.

@noindent
Bryan: Here is the thing, so people
always say `do not run as root.'
@emph{I always} run as root.

@noindent
Chris: Do you really always run as
root?

@noindent
Bryan: Hell yes. Do you know why I
always run as root?

@noindent
Chris: Why?

@noindent
Bryan: Awesome.

@noindent
Chris: Here, I... <interrupted>

@noindent
Bryan: I live on the edge. I'm like
Mad Max. <Saying something but Chris
is louder.>

@noindent
Chris: Do you really always run as
root for real?

@noindent
Bryan: No, I do not run as root.
Are you kidding me, that is asinine!
I would love to think that I am so
hardcore that I just always ran as
root. I just, caution to the wind,
screw it, lets just thunderdome this
bitch and... you know, see what
happens. But no, never run as root,
never ever do that. The only time
you run as root is when you run as
root temporarly, you sudo.

@noindent
Chris: You need to do something.
@end cartouche

Only use @command{reset} if you
are absolutely sure and know exactly
what you are doing.



@node I just don't know what went wrong
@chapter I just don't know what went wrong

@menu
* Naïve reset::
* Using the stash::
* Commit amendment::
* Bisection::
@end menu



@node Naïve reset
@section Naïve reset

If something went horribly, horribly,
horribly, horribly wrong and you do
not know how to get back to a clean
state, you can always doing this naïvely
by clone the repository:

@example
git clone REPOSITORY REPOSITORY.new
cp REPOSITORY/.git/config REPOSITORY.new/.git/config
yes | rm -r REPOSITORY
mv REPOSITORY.new REPOSITORY
@end example



@node Using the stash
@section Using the stash

The stash is a grate utility for storing
changes. If you have made changes in
the working directory or the index, you
can store them in the stash and both
the working directory and the index will
be restored to the @code{HEAD}. Keep
in mind the the naïve reset will discard
the stash because the stash is local.
Changes stored to the stash can be applied
to any branch and any later state of the
@code{HEAD}, that is what the stash is
made for.

The basic stash operations include:

@table @command
@item git stash
Store the changes made to the index and
working directory.

@item git stash drop
Discard the object at the top of the
stash stack.

@item git stash apply
Apply changes stored as the object at the
top of the stash stack.

@item git stash pop
Synonym for
@command{git stash apply && git stash drop}.

@item git stash clear
Discard all stored stash objects.
@end table



@node Commit amendment
@section Commit amendment

If you have not yet pushed your latest
commit you can amend it. If you have
pushed it, you cannot amend it cause
the commit ID changes because it is
SHA-1 hashsum of all imformation.

To amend your commit run
@command{git commit --amend}.
It will launch your text editor so
you can edit the commit message,
additionally all staged changes are
included in the amendment.



@node Bisection
@section Bisection

Bisection is the process of identifying
when a bug was introduced.

To start a bisection you first need
to tell git to start bisection and
specify the commit range. If the current
commit is bad you type:

@example
git bisect start
git bisect bad
git bisect good LAST_KNOWN_GOOD_COMMIT
@end example

After this you either of, depending if
the commit Git checks out is good or bad:

@example
git bisect good
git bisect bad
@end example

Git will tell you when it has found the
the first bad or possible first bad commit.
To then checkout the commit that was
checked out before the bisection started
type:

@example
git bisect reset
@end example

If you in the process of the bisection
landed on a commit you need to skip because
it has some other problem, you can use

@example
git reset --hard HEAD~N
@end example

Where @code{N} is the number of revisions
before the checked out, you want to jump to.
You can also use @command{git bisect skip}
to Git which revision that cannot be tested
so they are excluded from the bisection
process.

Instead of manually telling Git if a commit
is good or bad, you can use:

@example
git bisect run TEST_SCRIPT [ARGUMENTS...]
@end example

The test script should exit with 0, if and
only if the commit is good, 125 to skip the
commit, and anything else between 1 and
127, inclusively, if the commmit is bad.
Other values (128–255) will abort the
bisection.



@node Version control
@chapter Version control

@menu
* Tagging versions::
* Cherry picking::
* Examine the log::
@end menu



@node Tagging versions
@section Tagging versions

General, programs have different release
version. When you release a new version,
you tag the last commit makes it into
that version. To do this, create an
annotated tag object and push it to your
origin:

@example
git tag -a 'RELEASE_VERSION'
git push origin 'RELEASE_VERSION'
@end example

The created tag can be refered to as
any commit or branch.

If you want to remove a tag, you
just tell git to delete it and push
the deletion of its reference to
your origin:

@example
git tag -d 'RELEASE_VERSION'
git push origin :refs/tags/'RELEASE_VERSION'
@end example

@file{refs/tags/RELEASE_VERSION} is a
file in the @file{.git} directory.
Using a @code{:} tells git that you
want to push the local file before the
@code{:} to the remote file after the
@code{:}. If the local file is not
specified, in order words, the argument
begins with @code{:}, you are telling
git to remove the remote file.
This only work with referense, that is,
files inside @file{.git/refs}.



@node Cherry picking
@section Cherry picking

Cherry picking is the action of applying
changes made in another commit. It is a
create tool both for apply changes made
to another branch or to backport features.

Cherry picking works just merging branches,
except, instead of choosing a branch to pull
and apply all it changes you choose
individual commits, and commits ranges:

@example
git cherry-pick COMMIT_ID
@end example



@node Examine the log
@section Examine the log

So how are you going to cherry-pick commits
if you do not know their commit ID:s? Simple,
you use Git's log tool to find their ID:s.

The log will only show earlier commits in
the branch then the currently checked out
commit. Typing @command{git log} will show
you the commit's ID, author, date, and
commit message. You can limit the commits
to a commits where specify files has been
changed by appending those files to the
command.



@node Interface
@chapter Interface

@menu
* First things first::
* Wildcards::
@end menu



@node First things first
@section First things first

Many Git commands take both revisions
and paths as their arguments. First come
the revisions, then the files. If you
have files that can be misunderstood for
a revision, place a @option{--} between
the revisions and the files, anything
after a @option{--} is interpreted as
a file. It is a good practice to do this
in scripts that takes random user-input.



@node Wildcards
@section Wildcards

Many Git commands allow wildcards in
paths. These commands will expand
wildcards in the arguments just a
the shell. To avoid problems, never
use characters in paths that are
used in the shell for wildcards
and expansions... yeah, I know, it
is annoying.



@node Beyond Git
@chapter Beyond Git

@menu
* Additional tools::
* The binary problem::
* Writing commit messages::
* Standard files::
@end menu



@node Additional tools
@section Additional tools

Git is used for source control, for
a complete, possibily collaborative,
development environment you additional
tools.

Everything git can do, you can do in
the command line, but some repetitive
gets cumbersome in the command line
because you will need to run the same
command in unpredictable variations.
For this the package and command
@command{tig} may be just want you need
if you live in the terminal.

@command{bugseverywhere} is a grate tool
for keeping track of issues in git repositories.
Issues are commited to the current branch
you are working on, meaning that you can
have separate issues in separate branches.
So if you have separate branches for separate
features that are being implemented you can
create separate issues inside those branches.
And when a branch get merged with your develop
branch the unresolved issues is merged into
the develop branch.

If you are working on a large project with
multiple collaborator and contributors, and
you have dedicated hosting serve, you can
install Internet services that can assist
collaboration and especially contributors.
@itemize
@item
Flyspray is a web-based project management
and issue tracking system used by many projects
@item
GNU Mailman is a projcet for managing electronic
mailing lists which can be very useful for
accepting patches.
@item
newsd is standalone NNTP server for centralised
newsgroup forum serving on a single server, which
can be very discussions.
@end itemize

All of these programs, as well as Git, are
released under the GNU General Public License,
except Flyspray which is released under the GNU
Lesser General Public License.



@node The binary problem
@section The binary problem

Source control does not work well with binary
files. Consider that two persons are edition
the same file which cannot be interpreted by
a human using a text editor. If there is a
conflict, git may not realise it depending on
the binary format, or may not be able to merge
the changes. If git cannot merge the and you
cannot open it in a text editor, you will
not a file you can open and se the conflicts in
so you must open both's versions and manual
inspect and merge them.

Luckly most type of files formats have an
text based alternative.

@table @asis
@item Raster images
Portable pixmap (.ppm, .pgm, .pbm, .pnm) is
a text based@footnote{Optionally partially
binary} image format that is supported by
The GNU Image Manipulation Program (GIMP).

@item Vector images
Scalable Vector@footnote{Yes it is redudant,
but that is really what it is called} Graphics
(SVG) is the most popular vector image format,
and in fact it is text based, more precisely
it is XML based.
Will you may not be able to view an SVG file
with merge conflicts, you are still able to
open it in an text editor and fix the conficts.
However it may not be the simplest thing to
resolve in a text editor it helps you to identify
where the conflicts are located in the graphics.

@item Documentation
Texinfo and TeX are two very popular alternatives
to word editors such as Libre Office.

Texinfo is designed for manuals and books, and
can be compiled to virtually any publish format,
including @command{info} manuals, Hypertext
Markup Language, Portable Document Format and
PostScript.

TeX is more general purpose@footnote{Texinfo is
actually a macro set for TeX} has extensible and
redefinable syntax and is written to guarantee
that one source will always and everywhere produce
the exact same binaries, in terms of hows that
look when viewed. Its macro set LaTeX is the
prefered office system in academia.
@end table



@node Writing commit messages
@section Writing commit messages

Commits are accompanied by messages. This
both helps yourself and other developers to
identify a specific commit of interest, as
well as giving information about what is
happening in the development process, so
every developer can keep up to speed.

Commit messages can also be used to create
changelogs, where you create a change log
from the commit history and filter out
unimportant changes.

Change logs and commit massages are generally
written on the same style. A short message
written in imperfect, optionally with additional
larges paragraphs that goes more in depth.

Even if your project is not in English it
is preferable to keep your commit message
as well as much as possible of your project
(that is not visible to the user) in English.
Assume your project is in Swedish, everyone
that understands Swedish will be able to
translate it to any other language. So far
it would be okay to write anything in Swedish,
but once it has been translate, for example
to English, additional translators that do
not understand Swedish can contribute with
additional translators. Now it is perferable
with English, while the translators can
understand everything that are should translate
they do not understand anything else.
When translating a program it useful to be
able to understand what the program does and
not just want it prints so you can do more
accurate translations, and sometimes just
one translation is not enough to have en
unambiguous understanding.

It is preferable to commit as often as
possible, however this interrupts your
mind flow, so committing should take
as short time as possible@footnote{Git is
very friendly in this respect as create
a commit is lightning fast, and photon
fast in comparsing to other old school
source control systems}. Because of this
you may need to compromise your messages,
one thing you can do is to not describe
a fix bug if it should be obvious for
the changeset@footnote{Can only be obvious
from small changes}, after all if you
do not understand a change you can always
ask someone. Another thing you can do is
to use some standard shorthands.

@table @asis
@item m
Minor change.
@item doc
Add or change documentation.
@item typo
Fix a typo.
@item spello
Fix a spello.
@item grammaro
Fix a grammaro.
@item +
As well as, another logical change
in the same commit.
@end table

If you want shorten the time it takes to
create a commit, I personally recommend
to have a short shell function for opening
your text editor and stage the openned
files when the editor exits. And create a
shell function the runs
@command{git commit -m "$*"}.



@node Standard files
@section Standard files

All projects should have a set of files:

@table @asis
@item @file{README} @i{(optional)}
You should have a readme file at the root
of your project. It should describe the
project and how the program is used.

@item @file{DEPENDENCIES} @i{(optional)}
If your program has other dependencies
than a compiler, linker, interpreter,
@command{libc}, @command{coreutils} and
similar standard packages, and make tools
such as @command{make} and @command{automake}.
You should have a file that list all
dependency: runtime dependencies, optional
runtime dependencies, build dependencies,
opt-out build dependencies, opt-in build
dependencies. Try to specify version range
and what the package is used for, especially
for optional dependecies.

@item @file{INSTALLING} @i{(optional)}
For more advanced build systems you should
have a file that specified how to configure
the building process.

@item @file{CONTRIBUTING} @i{(optional)}
If your have rules on how to submit patches,
code style guildlines, or other information
for contributors, you should have files
with all such information in the top of
your repository.

@item @file{HACKING} @i{(optional)}
For complex project you can have a file
named @file{HACKING} with information
about how to modify the code.

@item @file{COPYING}
When you make your project available
it is not longer private software and
you need to give it a license compatible
with its dependencies. If you do not
have a license it defaults to being
proprietary. The copying file includes
the license summary or the complete
license text if it is short, and at
the top, the project name, short
description, years of active development,
and copyright holder name and e-mail
address. It is the same text as the
copyright information you put at the
top of source code files.

@item @file{LICENSE}
If the projects license is large, you
put the fill license plain text in the
file anmed @file{LICENSE} in the top
if your repository.
@end table



@node GNU Free Documentation License
@appendix GNU Free Documentation License
@include fdl.texinfo



@node Glossary
@appendix Glossary

@table @asis
@c TODO @item alternate object database

@item bare repositry
A bare repository is a repository without an
index tree or working tree. It just contains
the commits. Because it just contains the
commits it does not have a @file{.git} directory,
but instread directly contains the content
you would find in a @file{.git} directory.
If is normally named with @file{.git} is a
suffix.

@item blob object
Untyped object, for example, the contents of
a file.

@item branch
Alternative parallel development line, normally
indended the be merged with the branch it forked
out of.

@item cache
Obsolete, replaced by ‘index’.

@item chain
List of objects where each object has a reference
to the next object, its successor.

@item checkout
The action of changing branch.

@item cherry-picking
Creating a new commit from a subset of commits.

@item clean
A working tree is clean if has no changes
relative to the current @code{HEAD}

@item commit (noun)
A single point in the development history
stored in Git. The entire history of a project
is represented as a set of interrelated commits.

Alternatives to Git may use the terms `revision'
or `version' instead of `commit'. `Commit' is
also used as a short and for `commit object'.

@item commit (verb)
The action of storing a new snapshot of the
project's state. The state of the index is
stored and @code{HEAD} is advanced to the
new commit.

@item commit object
A Git internal object which contains the
information about a particalur revision.
It contains informations such as author,
commiter, date, files and parents.

@item core Git
The fundamental tools of source code management.

@item dangling object
An object that is not reachable, even from other
unreachable objects; there are not references to
it.

@item detached @code{HEAD}
@code{HEAD} that does not store the name of a
branch. Git allows you to checkout arbitrary
commmits, when you checkout a commit that is
not the tip of any branch, the @code{HEAD} is
``detached''.

To store changes make in a detached @code{HEAD}
you must first create a new branch from it.

@item directory
You may also know it as `catalogue' or even
`folder'. It can contain files and other
directories, which you can list with the
command @command{ls} and you can change directory
with the command @command{cd}.

@item dirty
The working tree is dirty if it contains uncommited
modifications.

@item evil merge
A merge that introduces changes that do not
appear in any parent. Variable name conflicts
can be a cause of evil merges. This is why you
do not rebase your commits. 

@item fast-forward
A special type of merge that will often be
the case when you pull updates from a remote
repository. A fast-forward merge is a merge
where you have made no changes but there
are changes on the remote-tracking branch
that can be pulled without any merge logic.

@item fetch
When you fetch a branch's head ref from a
remote repository, you download, to a local
database, objects that have not yet been
downloaded.

@item gitfile
A plain file named @file{.git} located in
the root fo the working tree, that points
the to real repository.
The is a create idea to use this if you
do not want a backup repostory as it prevents
you from accidentally remove anything but
the working tree.

@c TODO @item grafts

@item hash
Especially if cryptographic, almost unique,
indefeasibly reverable, fixed size, scrambling
of content. In Git's context, synonym for
object name.

@item head
A named reference to the commit at the tip
if a branch.

@item @code{HEAD}
The head of the currently checked out branch,
or the currently checkout commit in which case
the @code{HEAD} is ``detached''.

@item head ref
Synonym for `head'.

@item hook
Several Git commands make callouts to user
definable scripts. This allows developers to
add functionally or checkout, and commands
can be verified and aborted.

@file{.git/hooks} are filled with sample
scripts that can be enabled by removing their
@file{.sample} suffix.

@item index
Snapshot of the working tree intended to
be promoted to a commit.

@item index entry
The information regarding a particular file
that is stored in the index

@item master
Unless set otherwise, the default branch in
a repository. It is created with the first
commit in the project.

@c @item merge (verb)
@c @item merge (noun)
@c @item object
@c @item object database
@c @item object identifier
@c @item object name
@c @item object type

@item octopus
The action of mergin more than two branches.

@item origin
The default repository to push to, the one
you cloned.

@c @item pack
@c @item pack index
@c @item pathspec
@c @item pickaxe
@c @item plumbing
@c @item porcelain
@c @item pull
@c @item push
@c @item reachable
@c @item rebase
@c @item ref
@c @item reflog
@c @item refspec
@c @item remote-tracking branch
@c @item repository

@item resolve
The action of manually merging the parts
the tool could not automatically merge.

@item revision
A commit.

@item rewind
The action of throwing away part of the
development.

@item SHA-1
Secure Hash Algorithm 1, a cryptographic hash
function used by Git for object names. It is
the fastest secure hash algorithm around, bit
is is also quite old.

@item shallow repository
A repository with an incomplete commit history.

@c @item symref
@c @item tag
@c @item tag object
@c @item topic branch
@c @item tree
@c @item tree object
@c @item tree-ish
@c @item unmerged index
@c @item unreachable object
@c @item upstream branch
@c @item working tree
@end table

@bye