tests/test-empty-file.t

largefiles: always create the cache and standin directories when cloning

The standin matcher only works if the .hglf directory exists (and it won't exist
if 'clone -U' is used, unless --all-largefiles is also specified).  Since not
even 'update -r null' will get rid of the standin directory, this ensures that
the standin directory always exists if the repo has the 'largefiles'
requirement.  This requirement is only set after a largefile is committed, so
these directories will not be created for repos that have the extension enabled
but have not committed a largefile.

With the standin directory in place, 'lfconvert --to-normal' will now be able to
download the required largefiles when converting a repo that was created with
'clone -U', and whose files are not in the usercache.

The downloadlfiles command could probably be put inside the 'largefiles'
requirement conditional too, but given that the user specified --all-largefiles,
there is likely an expectation to print out the number of largefiles downloaded,
even if it is 0.

  $ hg init a
  $ cd a
  $ touch empty1
  $ hg add empty1
  $ hg commit -m 'add empty1'

  $ touch empty2
  $ hg add empty2
  $ hg commit -m 'add empty2'

  $ hg up -C 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ touch empty3
  $ hg add empty3
  $ hg commit -m 'add empty3'
  created new head

  $ hg heads
  changeset:   2:a1cb177e0d44
  tag:         tip
  parent:      0:1e1d9c4e5b64
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add empty3
  
  changeset:   1:097d2b0e17f6
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add empty2
  

  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

Before changeset 05257fd28591, we didn't notice the
empty file that came from rev 1:

  $ hg status
  M empty2
  $ hg commit -m merge
  $ hg manifest --debug tip
  b80de5d138758541c5f05265ad144ab9fa86d1db 644   empty1
  b80de5d138758541c5f05265ad144ab9fa86d1db 644   empty2
  b80de5d138758541c5f05265ad144ab9fa86d1db 644   empty3

  $ cd ..