- * Return the position of the start of the patch or the length of str if there
- * is no patch in the message.
+ * Find the end of the log message as an offset from the start of the input
+ * (where callers of this function are interested in looking for a trailers
+ * block in the same input). We have to consider two categories of content that
+ * can come at the end of the input which we want to ignore (because they don't
+ * belong in the log message):
+ *
+ * (1) the "patch part" which begins with a "---" divider and has patch
+ * information (like the output of git-format-patch), and
+ *
+ * (2) any trailing comment lines, blank lines like in the output of "git
+ * commit -v", or stuff below the "cut" (scissor) line.
+ *
+ * As a formula, the situation looks like this:
+ *
+ * INPUT = LOG MESSAGE + IGNORED
+ *
+ * where IGNORED can be either of the two categories described above. It may be
+ * that there is nothing to ignore. Now it may be the case that the LOG MESSAGE
+ * contains a trailer block, but that's not the concern of this function.