firefoxtree Mercurial extension enhances the interaction with
Background on Multiple Repositories¶
Firefox developers typically interact with multiple repositories. There is the canonical head of Firefox development, mozilla-central. There is one landing repositories called autoland autoland. Then there are release repositories like mozilla-beta, mozilla-release and mozilla-esr*,
All of these repositories share the same initial commit and thus are one logical repository. However, for historical and continuity reasons, the separate topological heads of this conceptual single repository are all stored in separate repositories on Mozilla’s servers.
Consolidating the Repositories Locally¶
Traditionally, Mozilla developers maintain separate clones of each
repository. There is thus a one to one mapping between local and remote
repositories. For example, you may have separate
autoland directories/clones to track the different upstream
repositories. This practice is grossly inefficient. The shared repository
data is fetched and stored multiple times. This creates more load for
the server, occupies more space on disk, and adds overhead to common
tasks such as rebasing from central to autoland.
The firefoxtree extension allows you to easily combine the separate remote repositories into a local, single, unified repository.
hg pull from a known Firefox repository, firefoxtree will
automatically create a local-only label corresponding to the name of the
remote repository. These labels will manifest as tags. For example:
$ hg pull https://hg.mozilla.org/mozilla-central pulling from https://hg.mozilla.org/mozilla-central searching for changes adding changesets adding manifests adding file changes added 130 changesets with 651 changes to 329 files (run 'hg update' to get a working copy) $ hg log -r tip changeset: 248552:d380166816dd tag: central tag: tip user: ffxbld date: Sat Nov 08 03:20:23 2014 -0800 summary: No bug, Automated blocklist update from host bld-linux64-spot-144 - a=blocklist-update
You can see from the output of
hg log that changeset
d380166816dd has the
central tag associated with it.
The following example demonstrates how to pull various Firefox repositories into a single local repository and then how to navigate between commits.:
$ hg pull https://hg.mozilla.org/integration/autoland pulling from https://hg.mozilla.org/integration/autoland searching for changes adding changesets adding manifests adding file changes added 34 changesets with 140 changes to 113 files (+1 heads) (run 'hg heads .' to see heads, 'hg merge' to merge) $ hg up central 327 files updated, 0 files merged, 10 files removed, 0 files unresolved $ hg log -r . changeset: 248552:d380166816dd tag: central tag: tip user: ffxbld date: Sat Nov 08 03:20:23 2014 -0800 summary: No bug, Automated blocklist update from host bld-linux64-spot-144 - a=blocklist-update $ hg up autoland 118 files updated, 0 files merged, 2 files removed, 0 files unresolved $ hg log -r . changeset: 248586:e021487d1297 tag: autoland user: Connor <email@example.com> date: Wed Oct 29 23:58:03 2014 -0400 summary: Bug 575094 - Modify how prefservice is accessed so that it's from the parent process and not from the child process. Also re-enable test_bug528292_wrap.js. r=jdm
If you are familiar with Git, it may help to think of these repository labels as remote refs.
To view a summary of which repositories are on which changesets, run
$ hg fxheads 248552:d380166816dd central No bug, Automated blocklist update from host bld-linux64-spot-144 - a=blocklist-update 248586:e021487d1297 autoland Bug 575094 - Modify how prefservice is accessed so that it's from the parent process and not from the child process. Also re-enable test_bug528292_wrap.js. r=jdm
The output of
hg fxheads is only current from the last time you
pulled from each repository. Given the frequency of pushes to the
Firefox repositories, at least one of your labels will likely be out
Pre-defined Repository Paths¶
Typically, if you are pulling from multiple remotes, you need to define
the names and URLs of those remotes in the
[paths] section of the
.hg/hgrc file. The names and URLs of Firefox
repositories are well-known, so firefoxtree does this for you.
hg pull <tree> to pull from a known Firefox repository.
$ hg pull central $ hg pull autoland
hg push <tree> to push to a Firefox repository (need permissions).:
$ hg push autoland
The registered name aliases should be intuitive. Try a name of a popular Firefox repository. It should just work. If you get stumped or want to see the full list of names, read the source.
The Special fxtrees Path¶
fxtrees path is special. If you
hg pull fxtrees, firefoxtree
will pull from all Firefox repositories that you have previously pulled
Typically, developers only care about a subset of all the Firefox
hg pull fxtrees provides a convenient mechanism to
only pull the repositories you have previously expressed an interest in
Other Special Paths¶
There are some special paths that expand to multiple repositories. If
hg pull with one of these paths, firefoxtree will iterate
through each of these repositories and pull from all of them. These
special paths include:
- Pull from all integration/landing repositories (autoland)
- Pull from all repositories that Firefox is released from (central, beta, release, esr, etc)
Safer Push Defaults¶
The default behavior of
hg push is to want to transfer all
non-remote changesets to the remote. In other words, if you have pulled
mozilla-central and mozilla-aurora into the same repository and you
hg push ssh://hg.mozilla.org/mozilla-central, Mercurial will want to
transfer all of mozilla-aurora’s changesets to central!
The way you are supposed to do this is to always pass a
-r argument to
hg push to tell Mercurial exactly what changesets
to push. Commonly, you want to push the working copy’s commit, so the
command to use would be
hg push -r . <remote>.
hg push -r . is almost always what is wanted when pushing to
a Firefox repository, firefoxtree automatically changes
to behave like
hg push -r . when pushing to a Firefox repository.
Working with Unified Repositories and Repository Labels¶
Astute readers may have noticed that Mercurial is reporting the
repository labels as tags. However, they don’t behave like tags.
.hgtags file is not updated and
hg push won’t transfer them.
Under the hood, the extension is using an extension-only feature of
Mercurial to supplement the tags list. The labels are being reported as
tags, but have almost nothing to do with actual tags.
The repository labels can only be modified by firefoxtree.
Furthermore, they are only modified when running
hg pull. Unlike
bookmarks or branches, user actions such as committing will not
advance the labels.