add "abbrev sha1 + blame view" in "push to review" dialog

[mo]

When editing code with F&T, one eventually ends up in the "Push to review" dialog where the user is asked to select a "fixup target" commit. In this dialog I would like two additions:

1. the dropdown currently has the commit subject lines of the existing non-fixup commits but it would be more useful if it had "ABBREV_SHA1 COMMIT_SUBJECT_LINE" entries instead (because in large reviews the user probably needs to look in "git blame" to figure what to target the fixup to and then he'll get the sha1 and not the subject line)

2. it would be nice to have the "git blame" of the edited lines available for each of the chunks that the user is about to commit (to make it even easier to select a fixup target).