The git-gui module cannot be wrapped like gitk, because the Tcl implementation
uses the program's basename to determine stuff like the name of the Window it
opens, etc., and it cannot deal with a program name that contain a dot, like
".git-gui-wrapped" did.
Instead of wrapping git-gui, it's now patched to execute 'wish' with a complete
store path.
While I was at it, I also applied this solution to git-gui--askpass.
svn path=/nixpkgs/trunk/; revision=25453
167f185411