On 5/30/2013 7:56 PM, Johnny Stenback wrote:
[TL;DR, I think we need to embrace git in addition to hg for
Firefox/Gecko hacking, what do you think?]
Personally, the more I use git, the more I hate it. But I also see that
other people love it...
* Developers can use git branches. They just work,
and they're a good alternative to patch queues.
I can't see how they are a good alternative. With patch queues, I can
maintain a complex refactoring in a patch queue containing dozens of
smallish patches. In particular, I can easily realize I made a mistake
in patch 3 while working on patch 21 and make sure that the fix ends up
in patch 3; I don't see how that is easily achievable in git branches.
* Developers can benefit from the better merge algorithms
used by git.
I don't know what you mean by that. Note that git's octopus merges are
not directly realizable in hg, so an hg-git bidirectional mirror may
need to ban such things in the incoming git.
* Git works well with Github, even though we're not switching
to Github as the ultimate source of truth (more on that below).
Outside of the community size, I personally can't see any benefits to
Github for Mozilla; if all you want is community outreach, you pretty
much just need a read-only git mirror on Github, which we already have.
Some of the known issues with embracing git are:
* Performance of git on windows is sub-optimal (we're
already working on it).
* Infrastructure changes needed...
* Retraining Mercurial developers to use git (if we went git-only)
* Porting all of our Mercurial customizations to git for a check-in head
* Updating all of our developer build documentation
* Adapting build processes to adjust to the git way of doing things
Option 1 is where I personally think it's worth investing effort. It
means we'd need to set up an atomic bidirectional bridge between hg and
git (which I'm told is doable, and there are even commercial solutions
for this out there that may solve this for us).
This is harder than it sounds: hg and git are subtly different in ways
that can seriously frustrate users if you don't pay attention. For
example (one that bit me very hard): hg records file copy/moves as part
of the changeset, while git attempts to reverse engineer them when it
needs to do so. So my attempt to merge my changes with a remote git
repository via hg-git failed miserably since the hg local repo didn't
catch the git moved repo. Mercurial also treats history as immutable, so
you can't push history revisions.
If all you need is a read-only mirror, these kind of changes aren't as
important (you're not going to damage official records, just
inconvenience some developers); for a two-way mirror, they are very much
worth considering.
--
Joshua Cranmer
Thunderbird and DXR developer
Source code archæologist
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