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

GIT suite has over 100 commands, and the manual page for each of
them discusses what the command does and how it is used in
detail, but until you know what command should be used in order
to achieve what you want to do, you cannot tell which manual
page to look at, and if you know that already you do not need
the manual.

Does that mean you need to know all of them before you can use
git?  Not at all.  Depending on the role you play, the set of
commands you need to know is slightly different, but in any case
what you need to learn is far smaller than the full set of
commands to carry out your day-to-day work.  This document is to
serve as a cheat-sheet and a set of pointers for people playing
various roles.

<<Basic Repository>> commands are needed by people who has 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
<<Individual Developer (Participant)>> section as well.

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

<<Repository Administration>> commands are for system
administrators who are responsible to care and feed git
repositories to support developers.


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

Everybody uses these commands to feed and care git repositories.

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

  * gitlink:git-fsck-objects[1] to validate the repository.

  * gitlink:git-prune[1] to garbage collect crufts in the
    repository.

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

Examples
~~~~~~~~

Check health and remove cruft.::
+
------------
$ git fsck-objects <1>
$ git prune
$ git count-objects <2>
$ git repack <3>
$ git prune <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
diskspace 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> after repack, prune removes the duplicate loose objects.
------------

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
and remove unneeded other packs
------------


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

A standalone individual developer does not exchange patches with
other poeple, 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-whatchanged[1] to find out where things have
    come from.

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

  * gitlink:git-add[1] and gitlink:git-update-index[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-pull[1] with "." as the remote to merge between
    local branches.

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

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

Examples
~~~~~~~~

Extract a tarball and create a working tree and a new repository to keep track of it.::
+
------------
$ tar zxf frotz.tar.gz
$ cd frotz
$ git-init-db
$ 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 <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 pull . 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 "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'.
<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 whatchanged -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> "pull" fetches from "origin" by default and merges.
<4> look at the changes since last time we checked, only in the
area we are interested in.
<5> fetch from a specific branch from a specific repository and 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/.git frotz <1>
satellite$ cd frotz
satellite$ cat .git/remotes/origin <2>
URL: mothership:frotz/.git
Pull: master:origin
satellite$ echo 'Push: master:satellite' >>.git/remotes/origin <3>
satellite$ edit/compile/test/commit
satellite$ git push origin <4>

mothership$ cd frotz
mothership$ git checkout master
mothership$ git pull . satellite <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 creates this file by default.  It arranges "git pull"
to fetch and store the master branch head of mothership machine
to local "origin" branch.
<3> arrange "git push" to push local "master" branch to
"satellite" branch of the mothership machine.
<4> push will stash our work away on "satellite" 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 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 master <7>
$ git pull . topic/one topic/two && git pull . 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 master.
<8> and bundle topic branches still cooking.
<9> backport a critical fix.
<10> create a signed tag.
<11> make sure I did not accidentally rewound 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: maint:refs/tags/ko-maint
Push: master
Push: +pu
Push: maint
<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
~~~~~~~~

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

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.
------------