tests/mockmakedate.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.

# mock out util.makedate() to supply testable values


import os

from mercurial import pycompat
from mercurial.utils import dateutil


def mockmakedate():
    filename = os.path.join(os.environ['TESTTMP'], 'testtime')
    try:
        with open(filename, 'rb') as timef:
            time = float(timef.read()) + 1
    except IOError:
        time = 0.0
    with open(filename, 'wb') as timef:
        timef.write(pycompat.bytestr(time))
    return (time, 0)


dateutil.makedate = mockmakedate