tests/test-double-merge.t

lfs: special case the null:// usercache instead of treating it as a url

The previous code worked on Windows, but not on Unix, and a pending patch's test
failed.  The url being used was something like "/tmp/.../client1/null://",
courtesy of ui.configpath().  Looking at the doc comment, this seems like it's
maybe not the right function to call (why should a relative cache path be
expanded relative to the repo root or config file?), but largefiles has been
using it since 8b8dd13295db (Oct 2011).  It was introduced in 1b591f9b7fd2 (Jan
2011) without comment or callers.  A grep over the whole history shows that only
largefiles used it until lfs and infinitepush came along recently.

It looks like if the `if not os.path.isabs(v) or "://" not in v` in configpath()
is changed to an 'and', both Linux and Windows are happy.  I'm guessing that
"://" is to pick off URLs, so that seems reasonable.  But I'm not sure why it
isn't explicitly "file://", and I thought that "file://foo" is relative anyway.
(At least, there are doctests for file:///tmp in util.url.)  There is no mention
of this setting in the help, but it is referenced on the wiki page for
largefiles.  (There's no mention that this is intended to be a URL, and the
example uses an absolute path.)

I don't want this blocking the rest of the lfs server discovery stuff.  It was
also wrong to allow a file:// URL here, but not in largefiles.

  $ 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
  starting 4 threads for background file closing (?)
   bar: remote copied from foo -> m (premerge)
  picked tool ':merge' for bar (binary False symlink False changedelete False)
  merging foo and bar to bar
  my bar@6a0df1dad128+ other bar@484bf6903104 ancestor foo@e6dc8efe11cc
   premerge successful
   foo: versions differ -> m (premerge)
  picked tool ':merge' for foo (binary False symlink False changedelete 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 ..