Mercurial is a source-code management tool which allows users to keep track of changes to the source code locally and share their changes with others. We use it for the development of Firefox.
Using hg clone¶
If you are not worried about network interruptions, then you can simply
use Mercurial to directly clone the repository you’re interested in
using its URL, as given below. For example, to use the command line to
mozilla-central into a directory called
you would use the following:
hg clone https://hg.mozilla.org/mozilla-central/ firefox-source cd firefox-source
Using Mercurial bundles¶
If you are worried that your Internet connection is not fast or robust enough to download such a large amount of data all in one go without being interrupted and cannot clone using the command given above, then you are recommended to try Mercurial bundles. If interrupted, they can be resumed (continued without downloading from the beginning) if the app you’re using to download supports it. For example, in Firefox you would right click on the download and select Resume once your connection to the Internet was reestablished.
You should configure Mercurial before submitting patches to Mozilla.
If you will be pulling the Firefox source code or one of the derived repositories, the easiest way to configure Mercurial is to run the vcs-setup mach command:
$ ./mach vcs-setup
This command starts an interactive wizard that will help ensure your Mercurial is configured with the latest recommended settings. This command will not change any files on your machine without your consent.
Other configuration tips¶
If you don’t have the Firefox source code available, you should edit your Mercurial configuration file to look like the following:
[ui] username = Your Real Name <email@example.com> merge = your-merge-program (or internal:merge) [diff] git = 1 showfunc = 1 unified = 8 [defaults] commit = -v
These settings can be added to
$HOME/.hgrc (Linux/macOS) or
You can configure the editor to use for commit messages using the editor option in the [ui] section or by setting the EDITOR environment variable.
If you are trying to access the repository through a proxy server, see these instructions
Selecting a repository (tree)¶
There are multiple hg repositories hosted at mozilla.org to choose from. A summary of the main trees is given below, but see https://hg.mozilla.org/ for the full list.
This is the main development tree for Firefox. Most developers write patches against mozilla-central.
The source for the current beta version of Firefox (and the next and all previous betas). This code represents the expected next release of the Firefox browser, and should be pretty stable.
The source for the current release of Firefox (and the next and all previous releases).
This is the integration tree for Firefox. Patches land in this repository first, and then are merged by the sheriffs in mozilla-central.
Mainly useful for localizers working on localizing Firefox. Code for all l10n projects lives here and is organized into separate repos that (in most cases) have the locale’s two character ISO code. To get the repo that you need look for the repo you’re interested in on the following page.
It is common for advanced users to want to interact with more than one firefox repository. If you get to the point where having individual copies of repositories is annoying you, then see https://mozilla-version-control-tools.readthedocs.org/en/latest/hgmozilla/unifiedrepo.html for instructions on doing this efficiently.
Selecting a revision to build¶
Most of the time the tip revision of most repositories will build without issue. If you are worried about it not, then you may want to get the latest revision that has passed the automatic tests.
By default with no configuration a similar-to-release build is done. If
you wish you can configure the build using a
Different OSs have different prerequisites for a successful build,
please refer to the build documentation
to verify they are available on your build machine.
There’s a number of extensions you can enable. See http://mercurial.selenic.com/wiki/UsingExtensions. Almost everyone should probably enable the following, most of them are enabled by
color - Colorize terminal output
histedit - Provides git rebase –interactive behavior.
rebase - Ability to easily rebase patches on top of other heads.
evolve - Enable and enhance the inprogress ChangesetEvolution work.
firefoxtree - Enhances the interaction with Firefox repositories.
These can all be turned on by just adding this to your .hgrc file:
[extensions] color = rebase = histedit = firefoxtree = evolve =
In addition, there are some 3rd party extensions that are incredibly useful for basic development:
Mozilla-specific functionality to aid in developing Firefox/Gecko.