Git merge messages and style

[Stuart Bishop]

pmr currently uses git default merges, which isn't great for automation. A merge may be fast forwarded, in which case the original commits and commit messages are included inline. Or more likely the branch needs merging which generates a commit with an uninformative message.

Instead, the commit message could be pulled from the Launchpad merge proposal field and either --no-ff or squash commits used (I personally prefer --no-ff). The commit message could be required for pmr to perform the merge, or fall back to the 'merge of commit-id' default (I'd go for required).