[PATCH v6 0/4] cat-file: add a '--literally' option

The changes made in this version are :

*  unpack_sha1_header_to_strbuf() now checks for Z_STREAM_END and also
the return is not changed to status (as per Junios suggestion) as this 
breaks the check done in sha1_loose_object_info() as the return is 
sometimes Z_BUF_ERROR (-5).

* In sha1_loose_object_info() if the status is set, then change the type 
to status. Also check for this in cat-file.c

* Add documentation and tests for the same.

Thanks for your suggestions.