Re: [PATCH/RFC] sequencer.c: record revert/cherry-pick commit with trailer lines

When a commit is reverted (or cherry-picked with -x) we add an English
sentence recording that commit id in the new commit message. Make
these real trailer lines instead so that they are more friendly to
parsers (especially "git interpret-trailers").

A reverted commit will have a new trailer

    Revert: <commit-id>

Similarly a cherry-picked commit with -x will have

    Cherry-Pick: <commit-id>
[...]
 I think standardizing how we record commit ids in the commit message
 is a good idea. Though to be honest this started because of my irk of
 an English string "cherry picked from..." that cannot be translated.
 It might as well be a computer language that happens to look like
 English.
[...]

@@ -1758,16 +1757,10 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
 		base_label = msg.label;
 		next = parent;
 		next_label = msg.parent_label;
-		strbuf_addstr(&msgbuf, "Revert \"");
-		strbuf_addstr(&msgbuf, msg.subject);
-		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
-		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
-
-		if (commit->parents && commit->parents->next) {
-			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
-			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
-		}
-		strbuf_addstr(&msgbuf, ".\n");
+		strbuf_addf(&msgbuf, "Revert \"%s\"\n\n", msg.subject);
+
+		strbuf_addf(&msgbuf, "Revert: %s\n",
+			    oid_to_hex(&commit->object.oid));
 	} else {
 		const char *p;