#762733 git: hold_lock_file_for_update should report error through a strbuf argument

#762733#5
Date:
2014-09-24 19:21:27 UTC
From:
To:
The hold_lock_file_for_update should return any helpful error string
using a strbuf argument.
This also means that unable_to_lock_message should be made private to
lockfile.c.