git-gui: Collapse $env(HOME) to ~/ in recent repositories on Windows
Apparently native Tcl/Tk on Windows is using \ as the return value from [file separator] but [file normalize] on that same system is using / rather than \ to represent a directory separator. I really think that is nuts, but its what is happening.
So we can actually just hardcode our separator to / as all systems we support (Windows, Mac OS X, UNIX) use /.
Signed-off-by: Shawn O. Pearce <firstname.lastname@example.org>