Everyday GIT With 20 Commands Or So
===================================

<<Basic Repository>> commands are needed by people who have a
repository --- that is everybody, because every working tree of
git is a repository.

In addition, <<Individual Developer (Standalone)>> commands are
essential for anybody who makes a commit, even for somebody who
works alone.

If you work with other people, you will need commands listed in
the <<Individual Developer (Participant)>> section as well.

People who play the <<Integrator>> role need to learn some more
commands in addition to the above.

<<Repository Administration>> commands are for system
administrators who are responsible for the care and feeding
of git repositories.


Basic Repository[[Basic Repository]]
------------------------------------

Everybody uses these commands to maintain git repositories.

  * gitlink:git-init[1] or gitlink:git-clone[1] to create a
    new repository.

  * gitlink:git-fsck[1] to check the repository for errors.

  * gitlink:git-prune[1] to remove unused objects in the repository.

  * gitlink:git-repack[1] to pack loose objects for efficiency.

  * gitlink:git-gc[1] to do common housekeeping tasks such as
    repack and prune.

Examples
~~~~~~~~

Check health and remove cruft.::
+
------------
$ git fsck <1>
$ git count-objects <2>
$ git repack <3>
$ git gc <4>
------------
+
<1> running without `\--full` is usually cheap and assures the
repository health reasonably well.
<2> check how many loose objects there are and how much
disk space is wasted by not repacking.
<3> without `-a` repacks incrementally.  repacking every 4-5MB
of loose objects accumulation may be a good rule of thumb.
<4> it is easier to use `git gc` than individual housekeeping commands
such as `prune` and `repack`.  This runs `repack -a -d`.

Repack a small project into single pack.::
+
------------
$ git repack -a -d <1>
$ git prune
------------
+
<1> pack all the objects reachable from the refs into one pack,
then remove the other packs.


Individual Developer (Standalone)[[Individual Developer (Standalone)]]
----------------------------------------------------------------------

A standalone individual developer does not exchange patches with
other people, and works alone in a single repository, using the
following commands.

  * gitlink:git-show-branch[1] to see where you are.

  * gitlink:git-log[1] to see what happened.

  * gitlink:git-checkout[1] and gitlink:git-branch[1] to switch
    branches.

  * gitlink:git-add[1] to manage the index file.

  * gitlink:git-diff[1] and gitlink:git-status[1] to see what
    you are in the middle of doing.

  * gitlink:git-commit[1] to advance the current branch.

  * gitlink:git-reset[1] and gitlink:git-checkout[1] (with
    pathname parameters) to undo changes.

  * gitlink:git-merge[1] to merge between local branches.

  * gitlink:git-rebase[1] to maintain topic branches.

  * gitlink:git-tag[1] to mark known point.

Examples
~~~~~~~~

Use a tarball as a starting point for a new repository.::
+
------------
$ tar zxf frotz.tar.gz
$ cd frotz
$ git-init
$ git add . <1>
$ git commit -m "import of frotz source tree."
$ git tag v2.43 <2>
------------
+
<1> add everything under the current directory.
<2> make a lightweight, unannotated tag.

Create a topic branch and develop.::
+
------------
$ git checkout -b alsa-audio <1>
$ edit/compile/test
$ git checkout -- curses/ux_audio_oss.c <2>
$ git add curses/ux_audio_alsa.c <3>
$ edit/compile/test
$ git diff HEAD <4>
$ git commit -a -s <5>
$ edit/compile/test
$ git reset --soft HEAD^ <6>
$ edit/compile/test
$ git diff ORIG_HEAD <7>
$ git commit -a -c ORIG_HEAD <8>
$ git checkout master <9>
$ git merge alsa-audio <10>
$ git log --since='3 days ago' <11>
$ git log v2.43.. curses/ <12>
------------
+
<1> create a new topic branch.
<2> revert your botched changes in `curses/ux_audio_oss.c`.
<3> you need to tell git if you added a new file; removal and
modification will be caught if you do `git commit -a` later.
<4> to see what changes you are committing.
<5> commit everything as you have tested, with your sign-off.
<6> take the last commit back, keeping what is in the working tree.
<7> look at the changes since the premature commit we took back.
<8> redo the commit undone in the previous step, using the message
you originally wrote.
<9> switch to the master branch.
<10> merge a topic branch into your master branch.
<11> review commit logs; other forms to limit output can be
combined and include `\--max-count=10` (show 10 commits),
`\--until=2005-12-10`, etc.
<12> view only the changes that touch what's in `curses/`
directory, since `v2.43` tag.


Individual Developer (Participant)[[Individual Developer (Participant)]]
------------------------------------------------------------------------

A developer working as a participant in a group project needs to
learn how to communicate with others, and uses these commands in
addition to the ones needed by a standalone developer.

  * gitlink:git-clone[1] from the upstream to prime your local
    repository.

  * gitlink:git-pull[1] and gitlink:git-fetch[1] from "origin"
    to keep up-to-date with the upstream.

  * gitlink:git-push[1] to shared repository, if you adopt CVS
    style shared repository workflow.

  * gitlink:git-format-patch[1] to prepare e-mail submission, if
    you adopt Linux kernel-style public forum workflow.

Examples
~~~~~~~~

Clone the upstream and work on it.  Feed changes to upstream.::
+
------------
$ git clone git://git.kernel.org/pub/scm/.../torvalds/linux-2.6 my2.6
$ cd my2.6
$ edit/compile/test; git commit -a -s <1>
$ git format-patch origin <2>
$ git pull <3>
$ git log -p ORIG_HEAD.. arch/i386 include/asm-i386 <4>
$ git pull git://git.kernel.org/pub/.../jgarzik/libata-dev.git ALL <5>
$ git reset --hard ORIG_HEAD <6>
$ git prune <7>
$ git fetch --tags <8>
------------
+
<1> repeat as needed.
<2> extract patches from your branch for e-mail submission.
<3> `git pull` fetches from `origin` by default and merges into the
current branch.
<4> immediately after pulling, look at the changes done upstream
since last time we checked, only in the
area we are interested in.
<5> fetch from a specific branch from a specific repository and merge.
<6> revert the pull.
<7> garbage collect leftover objects from reverted pull.
<8> from time to time, obtain official tags from the `origin`
and store them under `.git/refs/tags/`.


Push into another repository.::
+
------------
satellite$ git clone mothership:frotz frotz <1>
satellite$ cd frotz
satellite$ git config --get-regexp '^(remote|branch)\.' <2>
remote.origin.url mothership:frotz
remote.origin.fetch refs/heads/*:refs/remotes/origin/*
branch.master.remote origin
branch.master.merge refs/heads/master
satellite$ git config remote.origin.push \
           master:refs/remotes/satellite/master <3>
satellite$ edit/compile/test/commit
satellite$ git push origin <4>

mothership$ cd frotz
mothership$ git checkout master
mothership$ git merge satellite/master <5>
------------
+
<1> mothership machine has a frotz repository under your home
directory; clone from it to start a repository on the satellite
machine.
<2> clone sets these configuration variables by default.
It arranges `git pull` to fetch and store the branches of mothership
machine to local `remotes/origin/*` tracking branches.
<3> arrange `git push` to push local `master` branch to
`remotes/satellite/master` branch of the mothership machine.
<4> push will stash our work away on `remotes/satellite/master`
tracking branch on the mothership machine.  You could use this as
a back-up method.
<5> on mothership machine, merge the work done on the satellite
machine into the master branch.

Branch off of a specific tag.::
+
------------
$ git checkout -b private2.6.14 v2.6.14 <1>
$ edit/compile/test; git commit -a
$ git checkout master
$ git format-patch -k -m --stdout v2.6.14..private2.6.14 |
  git am -3 -k <2>
------------
+
<1> create a private branch based on a well known (but somewhat behind)
tag.
<2> forward port all changes in `private2.6.14` branch to `master` branch
without a formal "merging".


Integrator[[Integrator]]
------------------------

A fairly central person acting as the integrator in a group
project receives changes made by others, reviews and integrates
them and publishes the result for others to use, using these
commands in addition to the ones needed by participants.

  * gitlink:git-am[1] to apply patches e-mailed in from your
    contributors.

  * gitlink:git-pull[1] to merge from your trusted lieutenants.

  * gitlink:git-format-patch[1] to prepare and send suggested
    alternative to contributors.

  * gitlink:git-revert[1] to undo botched commits.

  * gitlink:git-push[1] to publish the bleeding edge.


Examples
~~~~~~~~

My typical GIT day.::
+
------------
$ git status <1>
$ git show-branch <2>
$ mailx <3>
& s 2 3 4 5 ./+to-apply
& s 7 8 ./+hold-linus
& q
$ git checkout -b topic/one master
$ git am -3 -i -s -u ./+to-apply <4>
$ compile/test
$ git checkout -b hold/linus && git am -3 -i -s -u ./+hold-linus <5>
$ git checkout topic/one && git rebase master <6>
$ git checkout pu && git reset --hard next <7>
$ git merge topic/one topic/two && git merge hold/linus <8>
$ git checkout maint
$ git cherry-pick master~4 <9>
$ compile/test
$ git tag -s -m "GIT 0.99.9x" v0.99.9x <10>
$ git fetch ko && git show-branch master maint 'tags/ko-*' <11>
$ git push ko <12>
$ git push ko v0.99.9x <13>
------------
+
<1> see what I was in the middle of doing, if any.
<2> see what topic branches I have and think about how ready
they are.
<3> read mails, save ones that are applicable, and save others
that are not quite ready.
<4> apply them, interactively, with my sign-offs.
<5> create topic branch as needed and apply, again with my
sign-offs.
<6> rebase internal topic branch that has not been merged to the
master, nor exposed as a part of a stable branch.
<7> restart `pu` every time from the next.
<8> and bundle topic branches still cooking.
<9> backport a critical fix.
<10> create a signed tag.
<11> make sure I did not accidentally rewind master beyond what I
already pushed out.  `ko` shorthand points at the repository I have
at kernel.org, and looks like this:
+
------------
$ cat .git/remotes/ko
URL: kernel.org:/pub/scm/git/git.git
Pull: master:refs/tags/ko-master
Pull: next:refs/tags/ko-next
Pull: maint:refs/tags/ko-maint
Push: master
Push: next
Push: +pu
Push: maint
------------
+
In the output from `git show-branch`, `master` should have
everything `ko-master` has, and `next` should have
everything `ko-next` has.

<12> push out the bleeding edge.
<13> push the tag out, too.


Repository Administration[[Repository Administration]]
------------------------------------------------------

A repository administrator uses the following tools to set up
and maintain access to the repository by developers.

  * gitlink:git-daemon[1] to allow anonymous download from
    repository.

  * gitlink:git-shell[1] can be used as a 'restricted login shell'
    for shared central repository users.

link:howto/update-hook-example.txt[update hook howto] has a good
example of managing a shared central repository.


Examples
~~~~~~~~
We assume the following in /etc/services::
+
------------
$ grep 9418 /etc/services
git             9418/tcp                # Git Version Control System
------------

Run git-daemon to serve /pub/scm from inetd.::
+
------------
$ grep git /etc/inetd.conf
git     stream  tcp     nowait  nobody \
  /usr/bin/git-daemon git-daemon --inetd --export-all /pub/scm
------------
+
The actual configuration line should be on one line.

Run git-daemon to serve /pub/scm from xinetd.::
+
------------
$ cat /etc/xinetd.d/git-daemon
# default: off
# description: The git server offers access to git repositories
service git
{
        disable = no
        type            = UNLISTED
        port            = 9418
        socket_type     = stream
        wait            = no
        user            = nobody
        server          = /usr/bin/git-daemon
        server_args     = --inetd --export-all --base-path=/pub/scm
        log_on_failure  += USERID
}
------------
+
Check your xinetd(8) documentation and setup, this is from a Fedora system.
Others might be different.

Give push/pull only access to developers.::
+
------------
$ grep git /etc/passwd <1>
alice:x:1000:1000::/home/alice:/usr/bin/git-shell
bob:x:1001:1001::/home/bob:/usr/bin/git-shell
cindy:x:1002:1002::/home/cindy:/usr/bin/git-shell
david:x:1003:1003::/home/david:/usr/bin/git-shell
$ grep git /etc/shells <2>
/usr/bin/git-shell
------------
+
<1> log-in shell is set to /usr/bin/git-shell, which does not
allow anything but `git push` and `git pull`.  The users should
get an ssh access to the machine.
<2> in many distributions /etc/shells needs to list what is used
as the login shell.

CVS-style shared repository.::
+
------------
$ grep git /etc/group <1>
git:x:9418:alice,bob,cindy,david
$ cd /home/devo.git
$ ls -l <2>
  lrwxrwxrwx   1 david git    17 Dec  4 22:40 HEAD -> refs/heads/master
  drwxrwsr-x   2 david git  4096 Dec  4 22:40 branches
  -rw-rw-r--   1 david git    84 Dec  4 22:40 config
  -rw-rw-r--   1 david git    58 Dec  4 22:40 description
  drwxrwsr-x   2 david git  4096 Dec  4 22:40 hooks
  -rw-rw-r--   1 david git 37504 Dec  4 22:40 index
  drwxrwsr-x   2 david git  4096 Dec  4 22:40 info
  drwxrwsr-x   4 david git  4096 Dec  4 22:40 objects
  drwxrwsr-x   4 david git  4096 Nov  7 14:58 refs
  drwxrwsr-x   2 david git  4096 Dec  4 22:40 remotes
$ ls -l hooks/update <3>
  -r-xr-xr-x   1 david git  3536 Dec  4 22:40 update
$ cat info/allowed-users <4>
refs/heads/master       alice\|cindy
refs/heads/doc-update   bob
refs/tags/v[0-9]*       david
------------
+
<1> place the developers into the same git group.
<2> and make the shared repository writable by the group.
<3> use update-hook example by Carl from Documentation/howto/
for branch policy control.
<4> alice and cindy can push into master, only bob can push into doc-update.
david is the release manager and is the only person who can
create and push version tags.

HTTP server to support dumb protocol transfer.::
+
------------
dev$ git update-server-info <1>
dev$ ftp user@isp.example.com <2>
ftp> cp -r .git /home/user/myproject.git
------------
+
<1> make sure your info/refs and objects/info/packs are up-to-date
<2> upload to public HTTP server hosted by your ISP.