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.

Back from London

I got back from London on Sunday from the Launchpad infrastructure sprint. Because of the terrorism scare, Heathrow was chaos (more so than usual). The bus service from the tube station to Terminal 4 ended up in a traffic jam. There were a lot of people milling around outside the terminal who were not being allowed in because they’d arrived too early (it was around 9am, and some of them had afternoon flights).

It took a while to find the end of the checkin queue because another queue (passport control) had extended in front of it. I got to the end of this other queue and was told that I needed to go to the other end of the terminal section to queue up. After an hour or so, I got to the head of the queue and was able to check in my luggage, saying good bye to my laptop, phone and other stuff I’d normally be carrying on board. I’d padded my bag with a few pillows and got the checkin lady to put “fragile” stickers over the bag, which was about as good as I could hope for.

Passengers queuing for checkin

Passengers queuing for checkin
My hand luggage

My clear plastic bag of hand luggage

Now it was time to queue for passport control. This queue had now extended out the door of the terminal and round the corner. The queue moved fairly slowly and it became apparent why once I got through: the security screening line started on the other side of the door and there wasn’t much room for new people to queue.

By the time I got to the security screening, it was almost midday. The screening involved X-raying of my clear plastic bag of hand luggage, belt and shoes. After walking through the metal detector, I got a pat down. At this point, they were confiscating dangerous contraband that people were trying to smuggle onto the plane such as glasses cases.

This left only about five minutes before the flight’s boarding was scheduled to close. Before boarding, they were checking people’s hand luggage to make sure passengers had receipts for any magazines or books from the airport bookshop, confiscating the items if the receipt couldn’t be found.

The actual flight ended up leaving about one and a half hours late after waiting for everyone to arrive (they ended up unpacking about 5 people’s luggage). I was resigned to the fact that I’d have to wait around Singapore airport for the next flight, since there was only one hour between landing and my connecting flight. Thankfully, Qantas delayed the flight to Perth though, so it was straight from one gate to another.

Things were pretty uneventful on getting back to Australia. There were no nasty surprises on opening my luggage — I assume the baggage handlers had been instructed to take special care of everyone’s luggage due to the UK restrictions.

Royal Victoria Dock, a few days before my flight. The towers at Canary Warf is visible on the horizon.