Retire git-unresolve and make it into "git-update-index --unresolve".
It processes all paths that follow.

During a merge, you would mark a path that is dealt with with:

	$ git update-index hello

and you would "undo" it with:

	$ git update-index --unresolve hello
Signed-off-by: NJunio C Hamano <junkio@cox.net>