tests/test-check-clang-format.t

lfs: add a local store method for opening a blob

The has() and read() methods already dynamically switch between the usercache
and local store.  This should generally be preferred to directly accessing the
vfs instances outside of the store.

The file is now explicitly opened in binary mode for clarity.  (It was also
being opened in binary mode before, but only because vfs.__call__() appends 'b'
if needed when not opening with 'text=True'.)

#require clang-format test-repo

  $ . "$TESTDIR/helpers-testrepo.sh"

  $ cd "$TESTDIR"/..
  $ for f in `testrepohg files 'set:(**.c or **.h) and not "listfile:contrib/clang-format-blacklist"'` ; do
  >   clang-format --style file $f > $f.formatted
  >   cmp $f $f.formatted || diff -u $f $f.formatted
  >   rm $f.formatted
  > done