The Third Bear

Just Right.

Integrating Trac and Gitolite: Round One

egj trac , gitolite , sysadmin

We're now going to set up the core integration between Trac and Gitolite, including:

  • Gitolite post-receive hooks to notify Trac of new commits
  • Trac components to update or close tickets when commit messages like "Fixes #1" are pushed to the git server
  • Trac Repository Browser for git repositories
Getting Permissions Right

The most involved bit here is ensuring that the filesystem permissions are all correct, and remain correct as files are edited and created by the software over time. Trac and Git both need some ability to read files from one another's directories. After this, the rest of the integration is pretty straightforward. Here's an overview of what permissions are needed:

  • For Trac to display files and changesets in its Repository Browser, the user running the Trac process needs read access to the objects in the relevant Git repositories.
  • For Gitolite's post-receive hook to notify Trac of new commits, the user running the Gitolite process needs read access to the relevant Trac instance's conf/trac.ini file; read and write access to the Trac instance's database; and read and write access to the Trac instance's logs.

The strategy we'll use is to add both the "trac" and "git" system users to a shared group, and ensure that all the files they need to share are owned by that group and group-readable.

As root:

groupadd infra
usermod -a -G infra trac
usermod -a -G infra git

Now we need to fix up the permissions in the Trac instance, and ensure that they remain fixed up even if Trac edits its own files (e.g. when you use the Admin Panels to edit your trac.iniconfiguration) --

su - trac
chown -R trac:infra sites
chmod g+r sites/test/conf/trac.ini
chmod -R g+w sites/test/db/  sites/test/log/
find /home/trac/sites/ -type d -exec chmod +s {} \;

We also need to fix up the permissions for both existing and new Gitolite repositories:

su - git
chown git:infra -R /home/git/repositories/
chmod -R g+rX /home/git/repositories/
find /home/git/repositories/ -type d -exec chmod +s {} \;
echo "21c21
<     UMASK                       =>  0077,
---
>     UMASK                       =>  0027,
" > /tmp/gitolite.rc.patch
patch /home/git/.gitolite.rc < /tmp/gitolite.rc.patch && rm /tmp/gitolite.rc.patch
Gitolite Post Receive Hook

As user "git", copy this script into /home/git/post-receive-trac and chmod +x it:

#! /usr/bin/python
# -*- coding: utf-8 -*-
#
# Copyright (c) 2011 Grzegorz Sobański
#
# Version: 2.0
#
# Git post receive script developed for mlabs
# - adds the commits to trac
# based on post-receive-email from git-contrib
#

import re
import os
import sys
from subprocess import Popen, PIPE, call

# config
with open("/home/git/TRAC_ENV") as config:
    TRAC_ENV = config.read.strip()
GIT_PATH = '/usr/bin/git'
TRAC_ADMIN = '/home/trac/web/ve/bin/trac-admin'
# if you are using gitolite or sth similar, you can get the repo name from environemt
REPO_NAME = os.getenv('GL_REPO')

# communication with git

def call_git(command, args, input=None):
    return Popen([GIT_PATH, command] + args, stdin=PIPE, stdout=PIPE).communicate(input)[0]


def get_new_commits(ref_updates):
    """ Gets a list uf updates from git running post-receive,
    we want the list of new commits to the repo, that are part
    of the push. Even if the are in more then one ref in the push.

    Basically, we are running:
    git rev-list new1 ^old1 new2 ^old2 ^everything_else

    It returns a list of commits"""

    all_refs = set(call_git('for-each-ref', ['--format=%(refname)']).splitlines())
    commands = []
    for old, new, ref in ref_updates:
        # branch delete, skip it
        if re.match('0*$', new):
            continue

        commands += [new]
        all_refs.discard(ref)

        if not re.match('0*$', old):
            # update
            commands += ["^%s" % old]
        # else: new - do nothing more

    for ref in all_refs:
        commands += ["^%s" % ref]

    new_commits = call_git('rev-list', ['--stdin', '--reverse'], '\n'.join(commands)).splitlines()
    return new_commits


def handle_trac(commits):
    if not (os.path.exists(TRAC_ENV) and os.path.isdir(TRAC_ENV)):
        print "Trac path (%s) is not a directory." % TRAC_ENV

    if len(commits) == 0:
        return

    args = [TRAC_ADMIN, TRAC_ENV, 'changeset', 'added', REPO_NAME] + commits 
    with open("/tmp/trac-gitolite.log", 'a') as fp:
        fp.write(' '.join(args))

    call(args)


# main
if __name__ == '__main__':
    # gather all commits, to call trac-admin only once
    lines = sys.stdin.readlines()
    updates = [line.split() for line in lines]
    commits = get_new_commits(updates)

    # call trac-admin
    handle_trac(commits)

Then, also add a file `/home/git/TRAC_ENV` with the following contents: `/home/trac/sites/test/`

That way, later on, we can easily change the Trac environment that the hook points to, without editing the hook script itself.

Then set up post-receive hooks on all repos to execute that script:

su - git
echo '#!/bin/sh

/home/git/post-receive-trac' > /home/git/.gitolite/hooks/common/post-receive && chmod +x /home/git/.gitolite/hooks/common/post-receive
./bin/gitolite setup --hooks-only

Now activate the Trac components to hook into that post-receive hook, and to enable a Git version-control backend:

su - trac
echo "[components]
tracopt.ticket.commit_updater.committicketreferencemacro = enabled
tracopt.ticket.commit_updater.committicketupdater = enabled
tracopt.versioncontrol.git.git_fs.csetpropertyrenderer = enabled
tracopt.versioncontrol.git.git_fs.gitconnector = enabled
tracopt.versioncontrol.git.git_fs.gitwebprojectsrepositoryprovider = enabled
" >> sites/test/conf/trac.ini
Making Sure It Works

To test it, we'll add Gitolite's "testing.git" repo to Trac:

su - trac
web/ve/bin/trac-admin sites/test repository add testing /home/git/repositories/testing.git

Through the web, create a ticket #1 in the Trac "test" environment. Then, on your local machine, clone the repo, add some code, and commit with -m "testing -- fixes #1" before pushing.

If all goes well, Trac's "Browser" tab will show your code and commits from the "testing" repo, and ticket #1 will now be closed.

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