tests/test-lfs-pointer.py

rust: simplify pattern file parsing

Previously we kept the pattern syntax as a &[u8] until the last
possible moment, which meant we had to handle potential errors when
parsing that &[u8].  But such errors could never actually occur, given
the structure of the code.

Now we parse it eagerly (in two places) and pass it around as a
PatternSyntax, so we can delete some error handling code.

parse_one_pattern is in particular useful for parsing patterns passed
on the command line, as we'll support later in this series.

# Import something from Mercurial, so the module loader gets initialized.
from mercurial import pycompat

del pycompat  # unused for now

from hgext.lfs import pointer


def tryparse(text):
    r = {}
    try:
        r = pointer.deserialize(text)
        print('ok')
    except Exception as ex:
        print((b'%s' % ex).decode('ascii'))
    if r:
        text2 = r.serialize()
        if text2 != text:
            print('reconstructed text differs')
    return r


t = (
    b'version https://git-lfs.github.com/spec/v1\n'
    b'oid sha256:4d7a214614ab2935c943f9e0ff69d22eadbb8f32b1'
    b'258daaa5e2ca24d17e2393\n'
    b'size 12345\n'
    b'x-foo extra-information\n'
)

tryparse(b'')
tryparse(t)
tryparse(t.replace(b'git-lfs', b'unknown'))
tryparse(t.replace(b'v1\n', b'v1\n\n'))
tryparse(t.replace(b'sha256', b'ahs256'))
tryparse(t.replace(b'sha256:', b''))
tryparse(t.replace(b'12345', b'0x12345'))
tryparse(t.replace(b'extra-information', b'extra\0information'))
tryparse(t.replace(b'extra-information', b'extra\ninformation'))
tryparse(t.replace(b'x-foo', b'x_foo'))
tryparse(t.replace(b'oid', b'blobid'))
tryparse(t.replace(b'size', b'size-bytes').replace(b'oid', b'object-id'))