Various fixes and cleanups.

I'll be sending these next:

  [PATCH] Help scripts that use git-rev-parse to grok args with SP/TAB/LF
  [PATCH] git-branch: avoid getting confused by empty or nonexisting branches.
  [PATCH] Audit rev-parse users.
  [PATCH] Install tools with "make install-tools".
  [PATCH] Test framework: prettyprint the failed command.
  [PATCH] git-clone-script: store where we cloned from in .git/branches/origin

They are various minor fixes and clean-ups.