completion: show can take both revlist and paths

The 'git show' completion uses __git_complete_file (aliased to
__git_complete_revlist_file), because accepts <tree-ish>:<path> as
well as <commit-ish>.  But the command also accepts range of commits
in A..B notation, so using __git_complete_revlist_file is more
appropriate.

There still remain two users of __git_complete_file, completions for
"archive" and "ls-tree".  As these commands do not take range
notation, and "git show" no longer uses __git_complete_file, the
implementation of it can be updated not to complete ranges, but that
is a separate topic.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -2360,7 +2360,7 @@ _git_show ()
 		return
 		;;
 	esac
-	__git_complete_file
+	__git_complete_revlist_file
 }
 
 _git_show_branch ()