git-reset: make it work from within a subdirectory.

If you typically sit in, say "src/", it's annoying to have to
change directory to do a reset.

This may need to be reworked when we add "git reset -- paths..."
to encapsulate the "ls-tree $tree | update-index --index-info"
pattern.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

git-reset.sh

 #!/bin/sh
 
 USAGE='[--mixed | --soft | --hard]  [<commit-ish>]'
+SUBDIRECTORY_OK=Yes
 . git-sh-setup
 
+TOP=$(git-rev-parse --show-cdup)
+if test ! -z "$TOP"
+then
+	cd "$TOP"
+fi
+
 update=
 reset_type=--mixed
 case "$1" in