Update emails to describe path using for_fork?

Forked MR's will print

Project:Branch <source_project_with_path>:<source_branch> -> <target_project_with_path>:<target_branch>

Non forked MR's will print

Branch <source_branch> -> <target_branch>

Change-Id: I89399aec2e7fde8e4b64b110a48099a95ae4f038