tests/test-issue612.t

store: replace invocation of "getsize()" by "vfs.stat()"

This patch replaces invocation of "getsize()", which calls "os.stat()"
internally, by "vfs.stat()".

The object referred by "self.rawvfs" is used internally by
"_fncachevfs" and doesn't encode filename for each file API invocation.

This patch invokes "os.stat()" via "self.rawvfs" to avoid redundant
filename encoding: invocation of "os.stat()" via "self.vfs" hides
filename encoding and encoding result from caller, so it is not
appropriate, when both encoded and non-encoded filenames should be
yield.

Even though changeset b42b0729744d improved stream_out performance by
"self.pathsep + path", this patch replaces it by
"os.path.join(self.base, path)" of vfs. So, this may increase cost to
join path components.

But this shouldn't have large impact, because:

  - such cost is much less than cost of "os.stat()" which causes
    system call invocation

  - "datafiles()" of store object is invoked only for "hg manifest
    --all" or "hg verify" which are both heavy functions

http://mercurial.selenic.com/bts/issue612

  $ hg init
  $ mkdir src
  $ echo a > src/a.c
  $ hg ci -Ama
  adding src/a.c

  $ hg mv src source
  moving src/a.c to source/a.c (glob)

  $ hg ci -Ammove

  $ hg co -C 0
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo new > src/a.c
  $ echo compiled > src/a.o
  $ hg ci -mupdate
  created new head

  $ hg status
  ? src/a.o

  $ hg merge
  merging src/a.c and source/a.c to source/a.c
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg status
  M source/a.c
  R src/a.c
  ? src/a.o