changing-files: add a shorthand property to check for copy relevant info

We are going to reuse this change in more place, so we factor it out first.

Differential Revision: https://phab.mercurial-scm.org/D9197

mercurial/changelog.py

@@ -583,13 +583,7 b' class changelog(revlog.revlog):'
         flags = 0
         sidedata = None
         if self._copiesstorage == b'changeset-sidedata':
-            if (
-                files.removed
-                or files.merged
-                or files.salvaged
-                or files.copied_from_p1
-                or files.copied_from_p2
-            ):
+            if files.has_copies_info:
                 flags |= flagutil.REVIDX_HASCOPIESINFO
             sidedata = metadata.encode_files_sidedata(files)
 

mercurial/metadata.py

@@ -75,6 +75,16 b' class ChangingFiles(object):'
             and self.copied_from_p2 == other.copied_from_p2
         )
 
+    @property
+    def has_copies_info(self):
+        return bool(
+            self.removed
+            or self.merged
+            or self.salvaged
+            or self.copied_from_p1
+            or self.copied_from_p2
+        )
+
     @util.propertycache
     def added(self):
         """files actively added in the changeset