builtin-rm: Add a --force flag

This adds a --force flag to git-rm, making it somewhat easier for
subversion people to switch.

Signed-off-by: Pieter de Bie <pdebie@ai.rug.nl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/git-rm.txt b/Documentation/git-rm.txt
index 4d0c495..5afb1e7 100644
--- a/Documentation/git-rm.txt
+++ b/Documentation/git-rm.txt
@@ -7,7 +7,7 @@
 
 SYNOPSIS
 --------
-'git rm' [-f] [-n] [-r] [--cached] [--ignore-unmatch] [--quiet] [--] <file>...
+'git rm' [-f | --force] [-n] [-r] [--cached] [--ignore-unmatch] [--quiet] [--] <file>...
 
 DESCRIPTION
 -----------
@@ -36,6 +36,7 @@
 	but this requires the `-r` option to be explicitly given.
 
 -f::
+--force::
 	Override the up-to-date check.
 
 -n::