Allow saving an object from a pipe

In order to support getting data into git with scripts, this adds a
--stdin option to git-hash-object, which will make it read from stdin.

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/Documentation/git-hash-object.txt b/Documentation/git-hash-object.txt
index db12e92..0924931 100644
--- a/Documentation/git-hash-object.txt
+++ b/Documentation/git-hash-object.txt
@@ -8,7 +8,7 @@
 
 SYNOPSIS
 --------
-'git-hash-object' [-t <type>] [-w] <file>
+'git-hash-object' [-t <type>] [-w] [--stdin] [--] <file>...
 
 DESCRIPTION
 -----------
@@ -29,6 +29,9 @@
 -w::
 	Actually write the object into the object database.
 
+--stdin::
+	Read the object from standard input instead of from a file.
+
 Author
 ------
 Written by Junio C Hamano <junkio@cox.net>