$ hg init repo

  $ cd repo

  $ echo line 1 > foo

  $ hg ci -qAm 'add foo'

copy foo to bar and change both files

  $ hg cp foo bar

  $ echo line 2-1 >> foo

  $ echo line 2-2 >> bar

  $ hg ci -m 'cp foo bar; change both'

in another branch, change foo in a way that doesn't conflict with

the other changes

  $ hg up -qC 0

  $ echo line 0 > foo

  $ hg cat foo >> foo

  $ hg ci -m 'change foo'

  created new head

we get conflicts that shouldn't be there

  $ hg merge -P

  changeset:   1:484bf6903104

  user:        test

  date:        Thu Jan 01 00:00:00 1970 +0000

  summary:     cp foo bar; change both

  $ hg merge --debug

    searching for copies back to rev 1

    unmatched files in other:

     bar

    all copies found (* = to merge, ! = divergent, % = renamed and deleted):

     src: 'foo' -> dst: 'bar' *

    checking for directory renames

  resolving manifests

   branchmerge: True, force: False, partial: False

   ancestor: e6dc8efe11cc, local: 6a0df1dad128+, remote: 484bf6903104

   preserving foo for resolve of bar

   preserving foo for resolve of foo

   bar: remote copied from foo -> m

  updating: bar 1/2 files (50.00%)

  picked tool 'internal:merge' for bar (binary False symlink False)

  merging foo and bar to bar

  my bar@6a0df1dad128+ other bar@484bf6903104 ancestor foo@e6dc8efe11cc

   premerge successful

   foo: versions differ -> m

  updating: foo 2/2 files (100.00%)

  picked tool 'internal:merge' for foo (binary False symlink False)

  merging foo

  my foo@6a0df1dad128+ other foo@484bf6903104 ancestor foo@e6dc8efe11cc

   premerge successful

  0 files updated, 2 files merged, 0 files removed, 0 files unresolved

  (branch merge, don't forget to commit)

contents of foo

  $ cat foo

  line 0

  line 1

  line 2-1

contents of bar

  $ cat bar

  line 0

  line 1

  line 2-2

  $ cd ..