Thanks to Bazaar's distributed model, you can get full access to the code of any branch hosted in Launchpad, with version control and history, right on your own machine.
That flexibility means you can start work on a project without having to get special permissions to commit code. Of course, if you make changes that you want to see integrated into the project's main line you need a way of telling the main line's owner that you want to merge.
Launchpad and Bazaar make that easy. Bazaar was made to merge: even complex merges can be relatively easy. Launchpad helps look after the community process of discussing whether a proposed merge is a good idea.
See also this description Code review relationships.
Proposing a merge
When you've come to a stage in your development where you're ready to merge your code into another branch registered against the project - such as its main line - you can make a public merge proposal.
To do so, visit your branch's overview page, click Propose for merging into another branch, then follow the on-screen instructions.
Now, Launchpad will notify the proposed target branch's owner of your proposal. Anyone viewing the overview page for your branch, or the target branch, will also see a link to view the details of your proposal.
You can also propose a merge by email by sending a merge directive to email@example.com.
In your email, you can ask for particular people to do the review by adding lines that say:
reviewer <name> where <name> is the Launchpad user name or email address of the reviewer.
You can ask for as many reviewers as you like. Note that you must start the command line with a space or your command will not be recognized.
The flow of this process
Understanding how the Code Review process works may be a little tricky to get the hang of, but once you have got the hang of it, then it's really easy. If you're new to this process, this is how it works:
- You submit your request to merge your branch into the main one (or whichever target branch interests you)
- Wait for one of the target branch's reviewers to review your code, they'll either:
- Accept your code, and it will be merged.
- Modify your code slightly, then merge it.
- Tell you what to do with a comment, marking your review as "Needs Fixing".
- If you're happy to, you do make the changes requested and push them into your branch. Then comment back on your proposal that you have done that. You should now await further action.
- Reject the changes. At this point, you can either try again discuss with the branch owner how to make your changes acceptable or continue work in your own branch.
Once you've proposed a merge, anyone who has a Launchpad account can comment and vote on the proposal. Taking part in a code review is virtually hassle-free:
no barriers: anyone can take part, so long as they have a Launchpad account
convenient: you can get updates and contribute using email, as well as the web interface.
Each review consists of votes - approve, abstain or disapprove - and a threaded conversation much as you might find on a web forum or a mailing list. If you're already familiar with Launchpad Bugs, you'll be right at home with code reviews.
As a subscriber to the branch or a participant in the code review, you'll receive email updates each time someone adds a vote or message to the review. Just as with the bug tracker, you can take part in the review both by visiting Launchpad's web interface and by replying to any of the emails you receive. In effect, each code review becomes an ad-hoc mailing list that exists for the lifetime of the review.
If you want to make your vote specific to one aspect of the proposed merge, you can add a tag. For example: if you wanted to vote disapprove, based on the user interface, you could add a tag of ui.
For an example of a review, take a look at a code review in the Storm project.
Using the code review email interface is straightforward. Reply to an email from the code review and your comment is added to the discussion in Launchpad.
If you want to include commands to modify the approval or status of the review you must either sign your email with your GPG key that is associated with your Launchpad account, or send through a trusted DKIM sender such as GMail.
Here is the list of available commands:
Note that you must start the command line with a space or your command will not be recognized.
review - inform the developer what you think of their changes
review approve - approve the change (alias: +1)
review disapprove - disapprove of the change (alias: -1)
review abstain - abstain from deciding (alias: -0 and +0)
review resubmit - tell the developer to rework the change
review needs-fixing - tell the developer that a few things need improvement (alias: needsfixing and needs_fixing)
review needs-info - tell the developer that you need more information (alias: needsinfo and needs-information and needsinformation)
merge - either approve or reject the proposed change
merge approved - approve of the merge proposal (alias: approve)
merge rejected - reject the merge proposal (alias: reject)
reviewer - add a new reviewer to the merge proposal
reviewer <name> where <name> is the Launchpad user name or email address of the new reviewer.
vote (deprecated: use review)
status (deprecated: use merge)
You can combine commands, so if you wanted to vote disapprove, add a tag of UI, leave a comment, and reject the merge proposal, you'd write:
This is a sensible change but I find the user interface confusing. review disapprove UI merge rejected
If you simply want to approve the proposal, using merge approved will also implicitly add an equivalent review approve unless you specify a review command separately.
Making the merge
Once you're ready to merge another branch into yours, follow Bazaar's instructions on merging branches.
You can pick choose which parts of Launchpad you want to use. However, when you use different parts of Launchpad together you can make them work together. Let's look at how you can link bug report and blueprints to branches of code.