tests/test-empty-file.t

largefiles: fix commit of a directory with no largefile changes (issue4330)

When a directory is named in the commit file list, the previous behavior was to
walk the list, and if no normal files in the directory were also named, add the
corresponding standin for each largefile in that directory.  The directory is
then dropped from the list, so that committing a directory with no normal file
changes works.  It then added the corresponding standin directory for the first
largefile seen, by prefixing it with '.hglf/'.

The latter is unnecessary since each affected largefile is explicitly referenced
by its standin in the list.  It also caused an abort if there were no changed
largefiles in the directory, because none of its standins changed:

    abort: .hglf/foo/bar: no match under directory!

This list of files is used to tweak a matcher in lfutil.updatestandinsbymatch(),
which is what is passed to commit().

The status() call that is ultimately done in the commit code with this matcher
seems to have some OS specific differences.  It is not necessary to append '.'
for Windows to run the largefiles tests cleanly.  But if '.' is not added to the
list, the match function isn't called on Linux, so status() would miss any
normal files that were also in a named directory.  The commit then proceeds
without those normal files, or says "nothing changed" if there were no changed
largefiles in the directory.  This is not filesystem specific, as VFAT on Linux
had the same behavior as when run on ext4.  It is also not an issue with
lfilesrepo.status(), since that only calls the overridden implementation when
paths are passed to commit.  I dont have access to an OS X machine ATM to test
there.

Maybe there's a better way to do this.  But since the standin directory for the
first largefile was previously being added, and that caused the same walk in
status(), there's no preformance change to this.  There is no danger of
erroneously committing files in '.', because the original match function is
called, and if it fails, the lfutil.updatestandinsbymatch() tweaked matcher only
indicates a match if the file is in the list of standins- and '.' never is.  The
added tests confirm this.

  $ 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 ..