* 'master' of git://github.com/psionides/git-subtree:
improved rev_is_descendant_of_branch() function
added temporary test dirs to gitignore
added tests for recent changes
fixed bug in commit message for split
changed alias for --prefix from -p to -P
fix for subtree split not finding proper base for new commits
allow using --branch with existing branches if it makes sense
added -m/--message option for setting merge commit message
added -p alias for --prefix