[PATCH] pullrequests: add support for custom pull request id prefix

[Mads Kiilerich]

By the way ... it has been mentioned before that the term "pull request" 
is weird for most workflows.

Inspired by discussions with people at the Mercurial sprint, I think I 
am settling on using the term "series". It is all about presenting a 
series of changes / patches / changesets so they can be previewed, 
reviewed, commented on, approved or rejected, pulled and tested, 
rebased, grafted, "evolved" and whatever you can come up with.

/Mads