@@ -721,6 +721,110 @@ static int handle_content_merge(struct merge_options *opt,
/*** Function Grouping: functions related to directory rename detection ***/
+MAYBE_UNUSED
+static void get_renamed_dir_portion(const char *old_path, const char *new_path,
+ char **old_dir, char **new_dir)
+{
+ char *end_of_old, *end_of_new;
+
+ /* Default return values: NULL, meaning no rename */
+ *old_dir = NULL;
+ *new_dir = NULL;
+
+ /*
+ * For
+ * "a/b/c/d/e/foo.c" -> "a/b/some/thing/else/e/foo.c"
+ * the "e/foo.c" part is the same, we just want to know that
+ * "a/b/c/d" was renamed to "a/b/some/thing/else"
+ * so, for this example, this function returns "a/b/c/d" in
+ * *old_dir and "a/b/some/thing/else" in *new_dir.
+ */
+
+ /*
+ * If the basename of the file changed, we don't care. We want
+ * to know which portion of the directory, if any, changed.
+ */
+ end_of_old = strrchr(old_path, '/');
+ end_of_new = strrchr(new_path, '/');
+
+ /*
+ * If end_of_old is NULL, old_path wasn't in a directory, so there
+ * could not be a directory rename (our rule elsewhere that a
+ * directory which still exists is not considered to have been
+ * renamed means the root directory can never be renamed -- because
+ * the root directory always exists).
+ */
+ if (end_of_old == NULL)
+ return; /* Note: *old_dir and *new_dir are still NULL */
+
+ /*
+ * If new_path contains no directory (end_of_new is NULL), then we
+ * have a rename of old_path's directory to the root directory.
+ */
+ if (end_of_new == NULL) {
+ *old_dir = xstrndup(old_path, end_of_old - old_path);
+ *new_dir = xstrdup("");
+ return;
+ }
+
+ /* Find the first non-matching character traversing backwards */
+ while (*--end_of_new == *--end_of_old &&
+ end_of_old != old_path &&
+ end_of_new != new_path)
+ ; /* Do nothing; all in the while loop */
+
+ /*
+ * If both got back to the beginning of their strings, then the
+ * directory didn't change at all, only the basename did.
+ */
+ if (end_of_old == old_path && end_of_new == new_path &&
+ *end_of_old == *end_of_new)
+ return; /* Note: *old_dir and *new_dir are still NULL */
+
+ /*
+ * If end_of_new got back to the beginning of its string, and
+ * end_of_old got back to the beginning of some subdirectory, then
+ * we have a rename/merge of a subdirectory into the root, which
+ * needs slightly special handling.
+ *
+ * Note: There is no need to consider the opposite case, with a
+ * rename/merge of the root directory into some subdirectory
+ * because as noted above the root directory always exists so it
+ * cannot be considered to be renamed.
+ */
+ if (end_of_new == new_path &&
+ end_of_old != old_path && end_of_old[-1] == '/') {
+ *old_dir = xstrndup(old_path, --end_of_old - old_path);
+ *new_dir = xstrdup("");
+ return;
+ }
+
+ /*
+ * We've found the first non-matching character in the directory
+ * paths. That means the current characters we were looking at
+ * were part of the first non-matching subdir name going back from
+ * the end of the strings. Get the whole name by advancing both
+ * end_of_old and end_of_new to the NEXT '/' character. That will
+ * represent the entire directory rename.
+ *
+ * The reason for the increment is cases like
+ * a/b/star/foo/whatever.c -> a/b/tar/foo/random.c
+ * After dropping the basename and going back to the first
+ * non-matching character, we're now comparing:
+ * a/b/s and a/b/
+ * and we want to be comparing:
+ * a/b/star/ and a/b/tar/
+ * but without the pre-increment, the one on the right would stay
+ * a/b/.
+ */
+ end_of_old = strchr(++end_of_old, '/');
+ end_of_new = strchr(++end_of_new, '/');
+
+ /* Copy the old and new directories into *old_dir and *new_dir. */
+ *old_dir = xstrndup(old_path, end_of_old - old_path);
+ *new_dir = xstrndup(new_path, end_of_new - new_path);
+}
+
static void compute_rename_counts(struct diff_queue_struct *pairs,
struct strmap *dir_rename_count,
struct strset *dirs_removed)