Shared Branches using Bazaar and Launchpad

Earlier, David Allouche described how to host Bazaar branches on Launchpad. At the end, he alluded to the ability to create branches that can be committed to by anyone on a team. I'll describe how this works here.

Launchpad Teams

Launchpad allows people to organise themseleves into teams. Most of the things people can do in Launchpad can also be done by teams, including owning branches.

You can create a new team at the following page:

https://launchpad.net/people/+newteam

There are three different membership policies you can choose from:

  • Open: anyone can join. Choosing this sort of team effectively gives everyone write access to branches owned by the team.
  • Moderated: new memberships must be approved by one of the administrators (this is the default policy). This makes it easy for people to request commit access to the branch while still requiring approval from a team administrator..
  • Restricted: new members can only be added by the team administrators. This is appropriate if new members shouldn't be able to propose themselves normally.

Once the team has been created, members of the team can create the branches.

Uploading a Team Owned Branch

Now that you are a member of a team, you can upload branches to that team's directory on bazaar.launchpad.net. This is done in the same way as uploading personal branches described in David's article:

cd branchdir
bzr push --create-prefix sftp://bazaar.launchpad.net/~teamname/product/branchname

When the command completes, the team owned branch will have been created. Now you can treat this branch like a personal branch, but once someone else pushes a commit to the branch, "bzr push" will tell you that the branch has diverged, and not let you push your changes until you merge them to your branch.

An alternative model is to use checkouts, which provide a workflow closer to CVS and Subversion without losing Bazaar's ability to work while disconnected.

Bazaar Checkouts

A Bazaar checkout is a local working copy bound to a remote branch such that changes are committed to the remote location. The remote branch data is also cached locally to speed up local operations and allow you to work while disconnected from the network. A checkout of the previously created team branch can be created with the following command:

bzr checkout sftp://bazaar.launchpad.net/~teamname/product/branchname team-branch
cd team-branch

Alternatively if you still have the local branch used to create the team branch, it can be converted to a checkout with the "bzr bind" command:

cd branchdir
bzr bind sftp://bazaar.launchpad.net/~teamname/product/branchname

You can then make commits to the checkout as you would with any other branch, provided the checkout is up to date with the remote branch. If another team member has committed to the branch in the mean time though, you will be prompted to update your checkout to the head of the latest version of the remote branch.

If this happens, the checkout can be updated by issuing the "bzr update" command. You can then retry the commit, after fixing any conflicts that are reported.

Disconnected Operation with Checkouts

If you are disconnected from the network, it will be impossible to publish your changes to the remote branch so running the "bzr commit" command on the checkout will fail.

To handle this situation, Bazaar lets you make local commits in your checkout. This is performed with the "bzr commit --local" command. You can treat these commits just like regular commits and get diffs between them, etc.

When you are connected to the network again, run "bzr update". This will pull in any changes made to the remote branch and turn your local commits into a pending merge. After fixing any conflicts (if there are any), running "bzr commit" will publish the changes to the remote branch for the world to see.

Feature Branches

If you are developing a feature that is not yet appropriate to check into the mainline team branch, the checkout workflow may not be convenient. In this case, it may make sense to create a personal branch to do the work and then merge the changes later on.

You can create a new branch using the "bzr branch" command. Since the checkout made previously contains full history data we can branch from it directly, which saves saves downloading the branch again:

bzr branch checkoutdir mybranch

If you want to make this branch available to others, it can be published to bazaar.launchpad.net as described in David's original article.

Merging your branch into the checkout is the same as merging into any other Bazaar branch:

bzr update
bzr merge mybranch
# resolve any conflicts that may be reported
bzr commit

Once the commit completes, the changes will be available on the team branch.

Conclusion

Without much trouble, you can create a shared mainline branch with Bazaar and Launchpad and use it in a way familiar to Subversion users. With one extra command you can extend the familiar model to allow commits while disconnected, providing the power of distributed revision control when you need it.