git_message_prettify

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.

@param out_ The user-allocated git_buf which will be filled with the cleaned up message.

@param message The message to be prettified.

@param strip_comments Non-zero to remove comment lines, 0 to leave them in.

@param comment_char Comment character. Lines starting with this character are considered to be comments and removed if strip_comments is non-zero.

@return 0 or an error code.