James Henstridge

When outlining the use of team branches on Launchpad previously, I used the --create-prefix option when pushing the branch to sftp://bazaar.launchpad.net. This was to make sure the initial push would succeed, even if the /~username/product directory the branch would be created in didn’t exist.

To simplify things for users, we made a change to the SFTP server in the latest release, so that --create-prefix is no longer necessary. This does not affect the allowed branch directories though: the structure is used to associate the branches with products, and decide who can write to the branches.

Another change included in the rollout is the ability to rename branches and reassign them to different owners through the web interface. So for instance, you can give ownership of a personal branch to a team your project grows to multiple developers. This should be used sparingly, since it will change the published branch URLs which can confuse people using your branch.

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.