getrenamedfn: get copy data from context object if configured

The function returned from getrenamedfn() calls
filelog.renamed(). That won't work when storing copy metadata in the
changeset.

I've just switched to a simple implementation here. We may or may not
need to optimize it later, possibly by optimizing the callers.

No more tests fail with "--extra-config-opt
experimental.copies.read-from=compatibility)" than they did before
this patch.

Differential Revision: https://phab.mercurial-scm.org/D6162

mercurial/scmutil.py

@@ -1205,6 +1205,18 b' def _markchanges(repo, unknown, deleted,'
             wctx.copy(old, new)
 
 def getrenamedfn(repo, endrev=None):
+    if repo.ui.config('experimental', 'copies.read-from') == 'compatibility':
+        def getrenamed(fn, rev):
+            ctx = repo[rev]
+            p1copies = ctx.p1copies()
+            if fn in p1copies:
+                return p1copies[fn]
+            p2copies = ctx.p2copies()
+            if fn in p2copies:
+                return p2copies[fn]
+            return None
+        return getrenamed
+
     rcache = {}
     if endrev is None:
         endrev = len(repo)