gitolite/README.mkd

# gitolite

Gitolite is the bare essentials of gitosis, with a completely different
config file that allows (at last!) access control down to the branch level,
including specifying who can and cannot *rewind* a given branch.  It is
released under GPL v2.  See COPYING for details.

In this document:

  * why
  * what's gone
  * what's new
  * the workflow

----

### why

I have been using gitosis for a while, and have learnt a lot from it.  But in
a typical $DAYJOB setting, there are some issues:

  * it's not always Linux; you can't just "urpmi gitosis" (or yum or apt-get)
    and be done
  * often, "python-setuptools" isn't installed (and on a Solaris9 I was trying
    to help remotely, we never did manage to install it eventually)
  * the most requested feature (see "what's new?") had to be written anyway

### what's gone

While I was pondering the need to finally learn python[1] , I also realised
that:

  * no one in $DAYJOB type environments will use or approve access methods
    that work without any authentication, so I didn't need gitweb/daemon
    support in the tool or in the config file
  * the idea that you admin it by pushing to a special repo is nice, but not
    really necessary because of how rarely these changes are made, especially
    considering how much code is involved in that piece

All of this pointed to a rewrite.  In perl, naturally :-)

### what's new

Per-branch permissions.  You will not believe how often I am asked this at
$DAYJOB.  This is almost the single reason I started *thinking* about rolling
my own gitosis in the first place.

It's not just "read-only" versus "read-write".  Rewinding a branch (aka "non
fast forward push") is potentially dangerous, but sometimes needed.  So is
deleting a branch (which is really just an extreme form of rewind).  I needed
something in between allowing anyone to do it (the default) and disabling it
completely (`receive.denyNonFastForwards` or `receive.denyDeletes`).

Take a look at the example config file in the repo to see how I do this.  I
copied the basic idea from `update-hook-example.txt` (it's one of the "howto"s
that come with the git source tree).  However, please note the difference in
the size and complexity of the *operational code* between the update hook in
that example, and in mine :-)  The reason is in the next section.

### the workflow

In order to get per-branch access, you *must* use an update hook.  However,
that only gets invoked on a push; "read" access still has to be controlled
right at the beginning, before git even enters the scene (just the way gitosis
currently works).

So: either split the access control into two config files, or have two
completely different programs *both* parse the same one and pick what they
want.  Crap... I definitely don't want the hook doing any parsing, (and it
would be nice if the auth-control program didn't have to either).

So I changed the workflow completely:

  * all admin changes happen *on the server*, in a special directory that
    contains the config and the users' pubkeys.  But there's no commit and
    push afterward
  * instead, after making changes, you "compile" the configuration.  This
    refreshes `~/.ssh/authorized_keys`, as well as puts a parsed form of the
    access list in a file for the other two pieces to use.

The pre-parsed form is basically a huge perl variable.  It's human readable
too (never mind what the python guys say!)

So the admin knows immediately if the config file had any problems, which is
good.  Also, the relatively complex parse code is not part of the actual
access control points, which are:

  * the program that is run via `~/.ssh/authorized_keys` (I call it
    `gl-auth-command`, equivalent to `gitosis-serve`); this decides whether
    git should even be allowed to run (basic R/W/no access)
  * the update-hook on each repo, which decides the per-branch permissions

### footnotes

[1] I hate whitespace to mean anything significant except for text; this is a
personal opinion *only*, so pythonistas please back off :-)

### contact

sitaramc@gmail.com