Canonical Voices

Posts tagged with 'git'


But I believe in this and it’s been tested by research
— The Clash, Death and Glory

Thanks to Norbert’s efforts, the LibreOffice project now has a Jenkins setup that not only gives us visibility on how healthy our master branch is, with the results being reported to the ESC regularly: In addition it allows everyone easily testing commits and branches on all major LibreOffice platforms (Linux, OS X, Windows) just by uploading a change to gerrit. Doing so is really easy once you are set up:

./logerrit submit                      # a little helper script in our repo
git push logerrit HEAD:refs/for/master # alternative: plain old git
git review                             # alternative: needs to install the git-review addon

Each of the above commands alone send your work for review and testbuilding to gerrit. The last one needs an additional setup, that is however really helpful and worth it for people working with gerrit from the command-line regulary.

So, what if you have a branch that you want to testbuild? Well, just pushing the branch to gerrit as suggested above still works: gerrit then will create a change for every commit, mark them as depending on each other and testbuild every commit. This is great for a small branch of a handful of commits, but will be annoying and somewhat wasteful for a branch with more than 10-15 commits. In the latter case you might not want a manual review for each commit and also not occupy our builders for each of them. So what’s the alternative, if you have a branch ${mybranch} and want to at least test the final commit to build fine everywhere?

git checkout -b ${mybranch}-ci ${mybranch} # switch to branch ${mybranch}-ci
git rebase -i remotes/logerrit/master      # rebase the branch on master interactively

Now your favourite editor comes up showing the commits of the branch. As your favourite editor will be vim, you can then type:

:2,$s/^pick/s/ | x

To squash all the commits of the branch into one commit. Then do:

git checkout -                                   # go back to whatever branch we where on before
git push logerrit ${mybranch}-ci:refs/for/master # push squashed branch to gerrit for testbuilding
git branch -D ${mybranch}-ci                     # optional: delete squashed branch locally

Now only wait for the builder on Jenkins to report back. This allowed me to find out that our compiler on OS X didnt think of this new struct as a POD-type, while our compilers on Linux and Windows where fine with it (see: “Why does C++ require a user-provided default constructor to default-construct a const object?” for the gory details). Testbuilding on gerrit allowed me to fix this before pushing something broken on a platform to master, which would have spoiled the nifty ability to test your commit before pushing for everyone else: Duly testing your commit on gerrit only to find that the master you build upon was broken by someone else on some platform is not fun.

The above allows you to ensure the end of your branch builds fine on all platforms. But what about the intermediate commits and our test-suites? Well, you can test that each and every commit passes tests quite easily locally:

git rebase -i remotes/logerrit/master --exec 'make check'

This rebases your branch on master (even if its already up to date) and builds and runs all the tests on each commit along the way. In case there is a test breakage, git stops and lets you fix things (just like with traditional troubles on rebases like changes not applying cleanly).

Note: gerrit will close the squashed branch change if you push the branch to master: The squashed commit message ends with the Change-Id of the final commit of the branch. So once that commit is pushed, the gerrit closes the review for the squashed change.

Another note: If the above git commands are too verbose for you (they are for me), consider using gitsh and aliases. Combined they help quite a lot in reducing redundant typing when working with git.

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David Murphy (schwuk)

I was browsing Twitter last night when Thoughbot linked to their post about commit messages.

This was quite timely as my team has been thinking about improving the process of creating our release notes, and it has been proposed that we generate them automatically from our commit messages. This in turn requires that we have commit messages of sufficient quality, which – to be honest – we don’t always. So the second proposal is to enforce “good” commit messages as part of reviewing and approving merge proposals into our projects. See this post from Kevin on my team for an overview of our branching strategies to get an idea of how our projects are structured.

We still need to define what constitutes a “good” message, but we will certainly use both the article from Thoughtbot and the oft-referenced advice from Tim Pope as our basis. We are also only planning to apply this to commits to trunk because, well, you don’t need a novel – or even a short story – for every commit in your spike branch!

Now, back to the Thoughtbot article, and this piece of advice stood out for me:

Never use the -m <msg> / --message=<msg> flag to git commit.

Since I first discovered -m I have used it almost exclusively, thinking I’m being so clever and efficient, but in reality I’ve been restricting what I could say to what felt “right” on an 80 character terminal. If nothing else, I will be trying to avoid the use of -m from now on.

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I finally listened to Sebastien Bacher and applied for GNOME commit rights yesterday, after hassling Seb once more about committing an approved patch for me. Surprisingly, it only took some 4 hours until my application was approved and my account created, wow! Apparently 71 patches are enough. :-)

With my new powers, I fixed a crash in gdm, and applied two stragglers into gvfs’ build system today.

More to come!

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Ian Clatworthy

Are you a Bazaar fan and need some help explaining to others why Bazaar is cool? I published a document last week called Why switch to Bazaar? that may help. I’ve tried hard to present the big picture together with some concrete examples, explaining what we stand for and what that means to users, teams and communities in reality. Furthermore, if you tried Bazaar 1.x but found it too slow or inefficient, I’m sure you’ll find the Bazaar 2.0 benchmarks included in the document great news.

I hope you find the document interesting and food for thought. If there are any mistakes or you’ll like to translate the document to another language, please let me know.

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