labhub/assign: Support super-short issue ref

... of the form `#1234`.

Closes #167

plugins/labhub.py

@@ -266,9 +266,27 @@ def process_short_ref(issue_reference):
 
             return m.group(1), m.group(2), m.group(3)
 
+        # Extreme short issue reference (e.g. `#1234`)
+        def process_extreme_short_ref(issue_reference):
+            issue_rgx = r'#(\d+)'
+            issue_reference_match = re.fullmatch(rgx, issue_reference)
+
+            if issue_reference_match is None:
+                return None
+
+            roomname_rgx = r'(.+?)/(.+)'
+            roomname_match = re.fullmatch(
+                roomname_rgx, self.room.name, re.IGNORECASE)
+
+            if roommatch is None:
+                return None
+
+            return roommatch.group(1), roommatch.group(2), m.group(1)
+
         issue_processors = [
             process_full_url,
-            process_short_ref
+            process_short_ref,
+            process_extreme_short_ref
         ]
 
         for issue_processor in issue_processor: