rose_arch: print return code as part of event

This gives us better confidence when an archive command fails to do what
it does but still return zero.
rosa svn-post-commit: only trunk notification

Only notify `rose-suite.info` changes on trunk.
Merge pull request #1407 from matthewrmshin/fix-rosa-svn-post-commit-branch-notification

rosa svn-post-commit: only trunk notification
Merge pull request #1404 from matthewrmshin/rose_arch-print-ret-code

rose_arch: print return code as part of event