git-rev-parse --symbolic-full-name

The plumbing level can understand that the user meant
"refs/heads/master" when the user says "master" or
"heads/master", but there is no easy way for the scripts to
figure it out without duplicating the dwim_ref() logic.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rev-parse.txt

@@ -70,6 +70,13 @@ OPTIONS
 	possible '{caret}' prefix); this option makes them output in a
 	form as close to the original input as possible.
 
+--symbolic-full-name::
+	This is similar to \--symbolic, but it omits input that
+	are not refs (i.e. branch or tag names; or more
+	explicitly disambiguating "heads/master" form, when you
+	want to name the "master" branch when there is an
+	unfortunately named tag "master"), and show them as full
+	refnames (e.g. "refs/heads/master").
 
 --all::
 	Show all refs found in `$GIT_DIR/refs`.