[PATCH] gitk: Use git wrapper to run git-ls-remote.

[PATCH] gitk: Use git wrapper to run git-ls-remote.

For some reason, the Cygwin Tcl's `exec' command has trouble running
scripts.  Fix this by using the C `git' wrapper.  Other GIT programs run
by gitk are written in C already, so we don't need to incur a
performance hit of going via the wrapper (which I'll bet isn't pretty
under Cygwin).

Signed-off-by: Mark Wooding <mdw@distorted.org.uk>
Acked-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>