compat/basename: make basename() conform to POSIX

According to POSIX, basename("/path/") should return "path", not
"path/". Likewise, basename(NULL) and basename("") should both
return "." to conform.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: dscho

compat/basename.c

@@ -4,10 +4,24 @@
 char *gitbasename (char *path)
 {
 	const char *base;
-	skip_dos_drive_prefix(&path);
+
+	if (path)
+		skip_dos_drive_prefix(&path);
+
+	if (!path || !*path)
+		return ".";
+
 	for (base = path; *path; path++) {
-		if (is_dir_sep(*path))
-			base = path + 1;
+		if (!is_dir_sep(*path))
+			continue;
+		do {
+			path++;
+		} while (is_dir_sep(*path));
+		if (*path)
+			base = path;
+		else
+			while (--path != base && is_dir_sep(*path))
+				*path = '\0';
 	}
 	return (char *)base;
 }