merge-ort: optionally produce machine-readable output

merge-ort: optionally produce machine-readable output

With the new `detailed` parameter, a new mode can be triggered when
displaying the merge messages: The `detailed` mode prints NUL-delimited
fields of the following form:

	<path-count> NUL <path>... NUL <conflict-type> NUL <message>

The `<path-count>` field determines how many `<path>` fields there are.

The intention of this mode is to support server-side operations, where
worktree-less merges can lead to conflicts and depending on the type
and/or path count, the caller might know how to handle said conflict.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>