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>

commit.c

@@ -1769,7 +1769,7 @@ const char *find_commit_header(const char *msg, const char *key, size_t *out_len
  * Returns the number of bytes from the tail to ignore, to be fed as
  * the second parameter to append_signoff().
  */
-size_t ignore_non_trailer(const char *buf, size_t len)
+size_t ignored_log_message_bytes(const char *buf, size_t len)
 {
 	size_t boc = 0;
 	size_t bol = 0;