commit: ignore_non_trailer computes number of bytes to ignore

ignore_non_trailer() returns the _number of bytes_ that should be
ignored from the end of the log message. It does not by itself "ignore"
anything.

Rename this function to remove the leading "ignore" verb, to sound more
like a quantity than an action.

Signed-off-by: Linus Arver <linusa@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/commit.c b/builtin/commit.c
index 7da5f92..d1785d3 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -900,7 +900,7 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		strbuf_stripspace(&sb, '\0');
 
 	if (signoff)
-		append_signoff(&sb, ignore_non_trailer(sb.buf, sb.len), 0);
+		append_signoff(&sb, ignored_log_message_bytes(sb.buf, sb.len), 0);
 
 	if (fwrite(sb.buf, 1, sb.len, s->fp) < sb.len)
 		die_errno(_("could not write commit template"));