largefiles: adapt remotestore._getfile to batched statlfile
9e1616307c4c introduced batching of statlfile, but not all codepaths got
converted.
_getfile gave _stat garbage and got garbage back. The garbage didn't match the
expected error codes and was thus interpreted as success. It could thus end up
trying to fetch a largefile that didn't exist.
Instead we now pass _stat valid input and handle both correct and invalid
output correctly.
This makes the code work as intended ... but it would probably be better if it
didn't abort on missing largefiles, just like it happened to do before.
$ hg init repo
$ cd repo
$ touch foo
$ hg ci -Am 'add foo'
adding foo
$ hg up -C null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
this should be stored as a delta against rev 0
$ echo foo bar baz > foo
$ hg ci -Am 'add foo again'
adding foo
created new head
$ hg debugindex foo
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 0 ..... 0 b80de5d13875 000000000000 000000000000 (re)
1 0 24 ..... 1 0376abec49b8 000000000000 000000000000 (re)
$ cd ..