The user-allocated git_buf which will be filled with the cleaned up message.
The message to be prettified.
Non-zero to remove comment lines, 0 to leave them in.
Comment character. Lines starting with this character are considered to be comments and removed if strip_comments is non-zero.
0 or an error code.
Clean up excess whitespace and make sure there is a trailing newline in the message.
Optionally, it can remove lines which start with the comment character.