copies: enable dagcopytrace for duplicatecopies() to fix empty commit issue

Summary: The original copytrace was too slow, so it was disabled by default. This diff enables `dagcopytrace` (new fast copytrace) for duplicatecopies() to fix the empty commit issue.

Reviewed By: sggutier

Differential Revision: D46975341

fbshipit-source-id: 11219daee9e400a5ff1d8eda26fe17fbca5d5f12

eden/scm/edenscm/copies.py

@@ -927,16 +927,21 @@ def duplicatecopies(repo, wctx, rev, fromrev, skiprev=None):
     skiprev will not be duplicated, even if they appear in the set of
     copies between fromrev and rev.
     """
-    exclude = {}
-    if skiprev is not None and repo.ui.config("experimental", "copytrace") != "off":
-        # copytrace='off' skips this line, but not the entire function because
-        # the line below is O(size of the repo) during a rebase, while the rest
-        # of the function is much faster (and is required for carrying copy
-        # metadata across the rebase anyway).
-        exclude = pathcopies(repo[fromrev], repo[skiprev])
+    dagcopytrace = _get_dagcopytrace(repo, wctx, skiprev)
     for dst, src in pycompat.iteritems(pathcopies(repo[fromrev], repo[rev])):
-        # copies.pathcopies returns backward renames, so dst might not
-        # actually be in the dirstate
-        if dst in exclude:
+        if dagcopytrace and dagcopytrace.trace_rename(
+            repo[skiprev].node(), repo[fromrev].node(), dst
+        ):
             continue
         wctx[dst].markcopied(src)
+
+
+def _get_dagcopytrace(repo, wctx, skiprev):
+    """this is for fixing empty commit issue in non-IMM case"""
+    if (
+        skiprev is None
+        or wctx.isinmemory()
+        or not repo.ui.configbool("copytrace", "skipduplicatecopies")
+    ):
+        return None
+    return repo._dagcopytrace

eden/scm/tests/test-rebase-inmemory-nochanges.t

@@ -42,21 +42,12 @@
   rebasing 811ec875201f "b" (b)
   note: rebase of 811ec875201f created no changes to commit
 
-# Without IMM, this behavior is semi-broken: the commit is not rebased out and the
-# created commit is empty. (D8676355)
+# Without IMM, confirm empty commit issue (D8676355) is fixed
 
   $ cd ../without-imm
 
   $ setconfig 'rebase.experimental.inmemory=0'
+  $ setconfig 'copytrace.skipduplicatecopies=True'
   $ hg rebase -r b -d a
   rebasing 811ec875201f "b" (b)
-  warning: can't find ancestor for 'file_new' copied from 'file'!
-
-  $ hg export tip
-  # HG changeset patch
-  # User test
-  # Date 0 0
-  #      Thu Jan 01 00:00:00 1970 +0000
-  # Node ID 0fe513c05d7fe2819c3ceccb072e74940604af36
-  # Parent  24483d5afe6cb1a13b3642b4d8622e91f4d1bec1
-  b
+  note: rebase of 811ec875201f created no changes to commit