copies: don't include copies that are not in source in directory move

I've been working on a rewrite of mergecopies(). I compared the output
of the rewritten version with the current version. I noticed that
between FIREFOX_NIGHTLY_59_END and FIREFOX_BETA_60_BASE in the
mozilla-unified repo, there were many copies that the current version
detected that the rewritten version did not. One example was
js/src/gc/Iteration.h -> js/src/gc/PublicIterators.h. Then I realized
that js/src/gc/Iteration.h doesn't even exist in
FIREFOX_NIGHTLY_59_END.

This patch adds a filtering step for the "fullcopy" dict. It turns out
that that change also affects the test for issue5020 in
test-merge-criss-cross.t. The 'dm' action no longer happens there. At
first I thought that the test case change meant that this patch was
broken, but I think it's actually correct tha the 'dm' action should
not happen there. The result of the bid merge is still the same.

I suspect this filtering is a better solution for the issue than
41f6af50c0d8 (merge: fix crash on criss cross merge with dir move and
delete (issue5020), 2017-01-31). I also suspect that it was broken
just a few months earlier by a005c33d0bd7 (mergecopies: add logic to
process incomplete data, 2016-10-04). Note that bid merge had been
enabled for a few years at that point, since 19903277f035 (merge: use
bid merge by default (BC), 2014-10-01).

This patch is still just a workaround. It will be cleaned up soon
(with the rewrite of mergecopies()). But doing this in a separate
patch makes later patches easier to understand and gives a place to
explain why this is changing.

Differential Revision: https://phab.mercurial-scm.org/D6244

mercurial/copies.py

@@ -682,6 +682,11 b' def _fullcopytracing(repo, c1, c2, base)'
         if len(fl) == 2 and fl[0] == fl[1]:
             copy[fl[0]] = of # not actually divergent, just matching renames
 
+    # Sometimes we get invalid copies here (the "and not remotebase" in
+    # _checkcopies() seems suspicious). Filter them out.
+    for dst, src in fullcopy.copy().items():
+        if src not in mb:
+            del fullcopy[dst]
     if fullcopy and repo.ui.debugflag:
         repo.ui.debug("  all copies found (* = to merge, ! = divergent, "
                       "% = renamed and deleted):\n")

tests/test-merge-criss-cross.t

@@ -423,17 +423,10 b' Verify that the old context ancestor wor'
      d1/b
     unmatched files in other:
      d2/b
-    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
-     src: 'd1/b' -> dst: 'd2/b' 
-    checking for directory renames
-     discovered dir src: 'd1/' -> dst: 'd2/'
-     pending file src: 'd1/a' -> dst: 'd2/a'
-     pending file src: 'd1/b' -> dst: 'd2/b'
   resolving manifests
    branchmerge: True, force: False, partial: False
    ancestor: 11b5b303e36c, local: c0ef19750a22+, remote: 6ca01f7342b9
-   d2/a: remote directory rename - move from d1/a -> dm
-   d2/b: remote directory rename, both created -> m
+   d2/b: remote created -> g
   
   calculating bids for ancestor 154e6000f54e
     searching for copies back to rev 3
@@ -453,8 +446,7 b' Verify that the old context ancestor wor'
   auction for merging merge bids
    d1/a: consensus for r
    d1/b: consensus for r
-   d2/a: consensus for dm
-   d2/b: picking 'get' action
+   d2/b: consensus for g
   end of auction
   
    d1/a: other deleted -> r