Re: [PATCH v3 21/33] merge-recursive: add get_directory_renames()

> diff --git a/merge-recursive.c b/merge-recursive.c
> index 2f4f85314a..6a0a6d4366 100644
> --- a/merge-recursive.c
> +++ b/merge-recursive.c
> @@ -1384,6 +1384,132 @@ static struct diff_queue_struct *get_diffpairs(struct merge_options *o,
>  	return ret;
>  }
>  
> +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;
> +	int old_len, new_len;
> +
> +	*old_dir = NULL;
> +	*new_dir = NULL;
> +
> +	/* For
> +	 *    "a/b/c/d/foo.c" -> "a/b/something-else/d/foo.c"
> +	 * the "d/foo.c" part is the same, we just want to know that
> +	 *    "a/b/c" was renamed to "a/b/something-else"
> +	 * so, for this example, this function returns "a/b/c" in
> +	 * *old_dir and "a/b/something-else" in *new_dir.
> +	 *
> +	 * Also, 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 == NULL || end_of_new == NULL)
> +		return;
> +	while (*--end_of_new == *--end_of_old &&
> +	       end_of_old != old_path &&
> +	       end_of_new != new_path)
> +		; /* Do nothing; all in the while loop */
> +	/*
> +	 * We've found the first non-matching character in the directory
> +	 * paths.  That means the current directory we were comparing
> +	 * represents the rename.  Move end_of_old and end_of_new back
> +	 * to the full directory name.
> +	 */
> +	if (*end_of_old == '/')
> +		end_of_old++;
> +	if (*end_of_old != '/')
> +		end_of_new++;
> +	end_of_old = strchr(end_of_old, '/');
> +	end_of_new = strchr(end_of_new, '/');
> +
> +	/*
> +	 * It may have been the case that old_path and new_path were the same
> +	 * directory all along.  Don't claim a rename if they're the same.
> +	 */
> +	old_len = end_of_old - old_path;
> +	new_len = end_of_new - new_path;
> +
> +	if (old_len != new_len || strncmp(old_path, new_path, old_len)) {
> +		*old_dir = strndup(old_path, old_len);
> +		*new_dir = strndup(new_path, new_len);