git-gui 0.7.3

Linus recently pointed out that the blame viewer in git-gui 0.7.2 is useless, and the one parked seemingly indefinately in my pu branch was much better, and couldn't do any worse than 0.7.2's.

So here's git-gui 0.7.3, available in my maint branch:

  git://repo.or.cz/git-gui.git maint

for merging into the next public Git release.

Features since 0.7.2:

* New selection indication and softer colors.  This change is
  due to the efforts of Matthijs Melchior, and makes the main
  interface window slightly more pleasing to read.

* Vastly improved internal blame viewer.  The new viewer was
  incrementally improved, but in the end it amounted to a total
  rewrite by the time we reached the 0.7.3 release.

* Blame viewer now shows two blame passes side-by-side on the
  same file, giving the user fast access to original author and
  relocation author, for any line of the file.

* Mouse tooltips appear in the blame viewer when you mouse over
  a line of interest.

* Hyperlinks to original location are offered for both the original
  commit and the relocation commit in the blame viewer.

Bug fixes since 0.7.2:

* Allow creating a branch when none exists.  Previously we crashed
  if the repository had no local branches, but had a valid HEAD.

* Better handle internal Tk destroy messages sent to widgets;
  we used to terminate the entire git-gui process when any widget
  was destroyed.

* Minor font corrections, where git-gui was not honoring the user's
  configured preferences.