reimplement the unused-patches command for the CentOS layout

src/centpkg/__init__.py

@@ -291,6 +291,28 @@ class Commands(Commands):
     def prep(self, *args, **kwargs):
         raise NotImplementedError("prep is not yet implemented in centpkg")
 
-    def unused_patches(self, *args, **kwargs):
-        raise NotImplementedError("unused_patches is not yet implemented in centpkg")
+    def unused_patches(self):
+        """Discover patches checked into source control that are not used
+
+        Returns a list of unused patches, which may be empty.
+        """
+
+        # Create a list for unused patches
+        unused = []
+        # Get the content of spec into memory for fast searching
+        spec = open(self.spec, 'r').read()
+        # Replace %{name} with the package name
+        spec = spec.replace("%{name}", self.module_name)
+        # Replace %{version} with the package version
+        spec = spec.replace("%{version}", self.ver)
+
+        # Get a list of files tracked in source control
+        files = self.repo.git.ls_files('--exclude-standard').split()
+        for file in map(os.path.basename, files):
+            # throw out non patches
+            if not file.endswith(('.patch', '.diff')):
+                continue
+            if file not in spec:
+                unused.append(file)
+        return unused