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Re: [eclipse-dev] Platform/JDT/PDE Committers Please Read: Git development process
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> I was wondering if tagging process can be completely removed
Not completely. We should go for a "2 branches" approach, because there's
another reason for tagging explicitly:
6. To have a well-defined checkpoint for contributions to the I-build.
It's important that teams can decide explicitly what will end up in a
build. If the build process just starts off HEAD, then the integration
build input is not controlled any more, and every committer must be aware
that releasing anything on an I-build day is risky.
- The person doing the build input should have run all tests and should
only release a state for which the tests are green locally.
- Sometimes, we need "parallel" releases in multiple bundles that need to
be synchronized.
- Sometimes, we need a rebuild (which should be more stable and thus only
include changes for the broken contributions).
Markus
From:
Ian Bull <irbull@xxxxxxxxxxxxxxxxx>
To:
"General development mailing list of the Eclipse project."
<eclipse-dev@xxxxxxxxxxx>
Date:
2011-10-13 01:04
Subject:
Re: [eclipse-dev] Platform/JDT/PDE Committers Please Read: Git development
process
John,
I was having some similar thoughts over the Canadian Thanksgiving weekend.
In particular, I was wondering if tagging process can be completely
removed (or at least automated). We tag (using the current process) for 5
reasons (are there others?):
1. To double-check our build contributions.
2. To allow work to continue in HEAD without releasing it.
3. To distribute the workload because CVS tagging was really slow.
4. To provide 'reproducible builds' (you called this a superimposed
branch, which is a great analogy).
5. To set our qualifiers properly so if a bundle doesn't change, the
qualifier doesn't change.
Taking these in order:
1. This can be part of the build process. Hudson, for example, shows you
a list of commits since the last build. We could likely do something
similar.
2. IMHO this was never really a good idea. This broke down pretty quickly
when somebody else wanted to commit something to the bundle and have their
changes released. Using a separate branch or using concepts like git-flow
are much better solutions.
3. This is no longer an issue.
4. We would still tag our builds, just not our individual bundles.
Reproducing a build would simply involve building a different tag. Maybe
each team could contribute a branch to the build (master by default). So,
if the p2 team wanted to fix a problem in yesterdays IBuild, we branch off
that tag, fix it, and contribute the new branch. Likely our build process
could start with a tag command (tag IYYYYMMDD-HHMM)
5. This is the hardest one. I wonder if we could have the Jar comparator
do this for us? That is, if a bundle changes since the last commit, then
the qualifier is automatically update. Of course there is a chicken/egg
problem here, but if we don't include the version field in our
Comparator algorithm, it might just work.
Our current git scripts look for new commits, but that makes the
assumption that if the src doesn't change, then the binaries don't change.
That's a little short-sighted, especially when we build and use our own
compiler.
Anyways, just my thoughts after too much turkey and too much wine.
Cheers,
Ian
On Wed, Oct 12, 2011 at 11:18 AM, John Arthorne <John_Arthorne@xxxxxxxxxx>
wrote:
Now that we are becoming more familiar with Git, we should have a
discussion about our team development processes and consider changes that
are more suitable to our new tools. In particular, our existing release
process of tagging and map files were designed for the CVS world where
moving code between branches was painful. This process is not adapting
well to Git. For example, you can't reliably checkout a branch or tag that
matches what was in a given build, and there is no clear way to apply
release tags such as "R3_7_1" because no single commit is guaranteed to
represent the built contents of all bundles in that repository.
If you think about it, our map files effectively superimposed another
branch on HEAD, with the precise contents of that branch defined by the
map tags for each project. This allowed us to do things like proceed with
new work in HEAD without disrupting rebuilds, or revert a change by
altering the map file (because backing out changes that span multiple
files in CVS is painful). With Git, the more natural expression of this
setup is to have two branches: one for integration builds and one for
ongoing work that we want to test and share with other teams but not
submit to a build. It turns out that there is a popular Git development
process similar to this, called git-flow [1]. I think a simplified form of
git-flow would match our current development practices:
- Two main branches called "develop" and "master"
- All major feature work is first released to "develop"
- Each team periodically merges "develop" into master after performing
their appropriate checks and tests (similar to our current weekly tag and
release process)
- Integration builds automatically tag and build the contents of "master"
With this approach each tag on master represents a build. This makes it
easy for anyone to checkout the contents of any particular build even if
it spans multiple Git repositories. This also allows you to revert a build
submission or make a surgical fix for a rebuild without disrupting the
ongoing work in the develop branch. We could also adopt other aspects of
git-flow such as release branches for our end-game period, although I'm
not convinced we need it.
After that long-winded explanation, my request is that all teams think
about their development practices and how they can be adjusted or improved
in our new Git setup. Read up on git-flow and think about how it applies
to our development process. If you're interested you might also want to
look at other processes such as github-flow [2] for an alternate
viewpoint. Talk about it within your team, and we'll aim to have a general
discussion about it at next week's planning call (Wednesday October 19th,
11am EDT). If you don't normally join that call, send feedback to your
team lead, or you're welcome to join next week's call to chime in. I don't
think we'll arrive at a perfect development process overnight, but we can
start to make changes and refine it as we go forward.
[1] http://nvie.com/posts/a-successful-git-branching-model/
[2] scottchacon.com/2011/08/31/github-flow.html
John
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R. Ian Bull | EclipseSource Victoria | +1 250 477 7484
http://eclipsesource.com | http://twitter.com/eclipsesource
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