+static int is_scissors_line(const struct strbuf *line)
+{
+ size_t i, len = line->len;
+ int scissors = 0, gap = 0;
+ int first_nonblank = -1;
+ int last_nonblank = 0, visible, perforation = 0, in_perforation = 0;
+ const char *buf = line->buf;
+
+ for (i = 0; i < len; i++) {
+ if (isspace(buf[i])) {
+ if (in_perforation) {
+ perforation++;
+ gap++;
+ }
+ continue;
+ }
+ last_nonblank = i;
+ if (first_nonblank < 0)
+ first_nonblank = i;
+ if (buf[i] == '-') {
+ in_perforation = 1;
+ perforation++;
+ continue;
+ }
+ if (i + 1 < len &&
+ (!memcmp(buf + i, ">8", 2) || !memcmp(buf + i, "8<", 2))) {
+ in_perforation = 1;
+ perforation += 2;
+ scissors += 2;
+ i++;
+ continue;
+ }
+ in_perforation = 0;
+ }
+
+ /*
+ * The mark must be at least 8 bytes long (e.g. "-- >8 --").
+ * Even though there can be arbitrary cruft on the same line
+ * (e.g. "cut here"), in order to avoid misidentification, the
+ * perforation must occupy more than a third of the visible
+ * width of the line, and dashes and scissors must occupy more
+ * than half of the perforation.
+ */
+
+ visible = last_nonblank - first_nonblank + 1;
+ return (scissors && 8 <= visible &&
+ visible < perforation * 3 &&
+ gap * 2 < perforation);
+}
+