merge: avoid superfluous filemerges when grafting through renames (issue5407)

This is a fix for a regression introduced by the patches for issue4028.

The test changes are due to us doing fewer _checkcopies searches now, which
makes some test outputs revert to the pre-issue4028 behavior. That issue itself
remains fixed, we only skip copy tracing for files where it isn't relevant.
As a nice side effect, this makes copy detection much faster when tracing
backwards through lots of renames.

mercurial/copies.py

@@ -631,6 +631,10 b' def _checkcopies(ctx, f, m1, m2, base, t'
     backwards = not remotebase and base != tca and f in mb
     getfctx = _makegetfctx(ctx)
 
+    if m1[f] == mb.get(f) and not remotebase:
+        # Nothing to merge
+        return
+
     of = None
     seen = set([f])
     for oc in getfctx(f, m1[f]).ancestors():

tests/test-graft.t

@@ -181,9 +181,6 b' Graft out of order, skipping a merge and'
     searching for copies back to rev 1
     unmatched files in other (from topological common ancestor):
      c
-    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
-     src: 'c' -> dst: 'b' *
-    checking for directory renames
   resolving manifests
    branchmerge: True, force: True, partial: False
    ancestor: 4c60f11aa304, local: 6b9e5368ca4e+, remote: 97f8bfe72746
@@ -200,9 +197,6 b' Graft out of order, skipping a merge and'
     searching for copies back to rev 1
     unmatched files in other (from topological common ancestor):
      c
-    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
-     src: 'c' -> dst: 'b' *
-    checking for directory renames
   resolving manifests
    branchmerge: True, force: True, partial: False
    ancestor: 4c60f11aa304, local: 1905859650ec+, remote: 9c233e8e184d
@@ -1280,3 +1274,15 b' Check the results of the grafts tested'
   
   $ hg cat f2c
   c2e
+
+Check superfluous filemerge of files renamed in the past but untouched by graft
+
+  $ echo a > a
+  $ hg ci -qAma
+  $ hg mv a b
+  $ echo b > b
+  $ hg ci -qAmb
+  $ echo c > c
+  $ hg ci -qAmc
+  $ hg up -q .~2
+  $ hg graft tip -qt:fail

tests/test-merge-local.t

@@ -66,7 +66,7 b' Local merge with bad merge tool:'
   merging zzz1_merge_ok
   merging zzz2_merge_bad
   warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
-  2 files updated, 1 files merged, 2 files removed, 1 files unresolved
+  2 files updated, 1 files merged, 3 files removed, 1 files unresolved
   use 'hg resolve' to retry unresolved file merges
   [1]
 
@@ -104,7 +104,7 b' Local merge with conflicts:'
   merging zzz1_merge_ok
   merging zzz2_merge_bad
   warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
-  2 files updated, 1 files merged, 2 files removed, 1 files unresolved
+  2 files updated, 1 files merged, 3 files removed, 1 files unresolved
   use 'hg resolve' to retry unresolved file merges
   [1]
 

tests/test-up-local-change.t

@@ -242,4 +242,11 b' test updating backwards through a rename'
   -a
   +b
 
+test for superfluous filemerge of clean files renamed in the past
+
+  $ hg up -qC tip
+  $ echo c > c
+  $ hg add c
+  $ hg up -qt:fail 0
+
   $ cd ..