repopick: Allow to pick changes by URL

Change-Id: I51a7b006aae785c51302f1fbb49c9b5936bdba8f
diff --git a/build/tools/repopick.py b/build/tools/repopick.py
index 39a4957..c6f7fc7 100644
--- a/build/tools/repopick.py
+++ b/build/tools/repopick.py
@@ -264,8 +264,12 @@
         reviews = fetch_query(args.gerrit, args.query)
         change_numbers = sorted([str(r['number']) for r in reviews], key=int)
     if args.change_number:
+        change_url_re = re.compile('https?://.+?/([0-9]+(?:/[0-9]+)?)/?')
         for c in args.change_number:
-            if '-' in c:
+            change_number = change_url_re.findall(c)
+            if change_number:
+                change_numbers.extend(change_number)
+            elif '-' in c:
                 templist = c.split('-')
                 for i in range(int(templist[0]), int(templist[1]) + 1):
                     change_numbers.append(str(i))