convert: add a mode where mercurial_sink skips empty revisions. The getchanges function of some converter_source classes can return some false positives. I.e. they sometimes claim that a file "foo" was changed in some revision, even though its contents are still the same. convert_svn is particularly bad, but I think this can also happen with convert_cvs and, at least in theory, with mercurial_source. For regular conversions this is not really a problem - as long as getfile returns the right contents, we'll get a converted revision with the right contents. But when we use --filemap, this could lead to superfluous revisions being converted. Instead of fixing every converter_source, I decided to change mercurial_sink to work around this problem. When --filemap is used, we're interested only in revisions that touch some specific files. If a revision doesn't change any of these files, then we're not interested in it (at least for revisions with a single parent; merges are special). For mercurial_sink, we abuse this property and rollback a commit if the manifest text hasn't changed. This avoids duplicating the logic from localrepo.filecommit to detect unchanged files.

import getopt

def fancyopts(args, options, state):
    long = []
    short = ''
    map = {}
    dt = {}

    for s, l, d, c in options:
        pl = l.replace('-', '_')
        map['-'+s] = map['--'+l] = pl
        if isinstance(d, list):
            state[pl] = d[:]
        else:
            state[pl] = d
        dt[pl] = type(d)
        if (d is not None and d is not True and d is not False and
            not callable(d)):
            if s: s += ':'
            if l: l += '='
        if s: short = short + s
        if l: long.append(l)

    opts, args = getopt.getopt(args, short, long)

    for opt, arg in opts:
        if dt[map[opt]] is type(fancyopts): state[map[opt]](state, map[opt], arg)
        elif dt[map[opt]] is type(1): state[map[opt]] = int(arg)
        elif dt[map[opt]] is type(''): state[map[opt]] = arg
        elif dt[map[opt]] is type([]): state[map[opt]].append(arg)
        elif dt[map[opt]] is type(None): state[map[opt]] = True
        elif dt[map[opt]] is type(False): state[map[opt]] = True

    return args