ydiff/cdiff.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
Term based tool to view *colored*, *incremental* diff in a *Git/Mercurial/Svn*
workspace or from stdin, with *side by side* and *auto pager* support. Requires
python (>= 2.5.0) and ``less``.
"""

import sys
import os
import re
import signal
import subprocess
import select
import difflib

META_INFO = {
    'version'     : '1.0',
    'license'     : 'BSD-3',
    'author'      : 'Matthew Wang',
    'email'       : 'mattwyl(@)gmail(.)com',
    'url'         : 'https://github.com/ymattw/cdiff',
    'keywords'    : 'colored incremental side-by-side diff',
    'description' : ('View colored, incremental diff in a workspace or from '
                     'stdin, with side by side and auto pager support')
}

if sys.hexversion < 0x02050000:
    raise SystemExit("*** Requires python >= 2.5.0")    # pragma: no cover

# Python < 2.6 does not have next()
try:
    next
except NameError:
    def next(obj):
        return obj.next()

try:
    unicode
except NameError:
    unicode = str

COLORS = {
    'reset'         : '\x1b[0m',
    'underline'     : '\x1b[4m',
    'reverse'       : '\x1b[7m',
    'red'           : '\x1b[31m',
    'green'         : '\x1b[32m',
    'yellow'        : '\x1b[33m',
    'blue'          : '\x1b[34m',
    'magenta'       : '\x1b[35m',
    'cyan'          : '\x1b[36m',
    'lightred'      : '\x1b[1;31m',
    'lightgreen'    : '\x1b[1;32m',
    'lightyellow'   : '\x1b[1;33m',
    'lightblue'     : '\x1b[1;34m',
    'lightmagenta'  : '\x1b[1;35m',
    'lightcyan'     : '\x1b[1;36m',
}

# Keys for revision control probe, diff and log with diff
VCS_INFO = {
    'Git': {
        'probe': ['git', 'rev-parse'],
        'diff': ['git', 'diff', '--no-ext-diff'],
        'log': ['git', 'log', '--patch'],
    },
    'Mercurial': {
        'probe': ['hg', 'summary'],
        'diff': ['hg', 'diff'],
        'log': ['hg', 'log', '--patch'],
    },
    'Svn': {
        'probe': ['svn', 'info'],
        'diff': ['svn', 'diff'],
        'log': ['svn', 'log', '--diff', '--use-merge-history'],
    },
}


def colorize(text, start_color, end_color='reset'):
    return COLORS[start_color] + text + COLORS[end_color]


def strsplit(text, width):
    r"""strsplit() splits a given string into two substrings, respecting the
    escape sequences (in a global var COLORS).

    It returns 3-tuple: (first string, second string, number of visible chars
    in the first string).

    If some color was active at the splitting point, then the first string is
    appended with the resetting sequence, and the second string is prefixed
    with all active colors.
    """
    first = ''
    second = ''
    found_colors = []
    chars_cnt = 0
    bytes_cnt = 0
    while len(text) > 0:
        # First of all, check if current string begins with any escape
        # sequence.
        append_len = 0
        for color in COLORS:
            if text.startswith(COLORS[color]):
                if color == 'reset':
                    found_colors = []
                else:
                    found_colors.append(color)
                append_len = len(COLORS[color])
                break

        if append_len == 0:
            # Current string does not start with any escape sequence, so,
            # either add one more visible char to the "first" string, or
            # break if that string is already large enough.
            if chars_cnt >= width:
                break
            chars_cnt += 1
            append_len = 1

        first += text[:append_len]
        text = text[append_len:]
        bytes_cnt += append_len

    second = text

    # If the first string has some active colors at the splitting point,
    # reset it and append the same colors to the second string
    if len(found_colors) > 0:
        first += COLORS['reset']
        for color in found_colors:
            second = COLORS[color] + second

    return (first, second, chars_cnt)


def strtrim(text, width, wrap_char, pad):
    r"""strtrim() trims given string respecting the escape sequences (using
    strsplit), so that if text is larger than width, it's trimmed to have
    width-1 chars plus wrap_char. Additionally, if pad is True, short strings
    are padded with space to have exactly needed width.

    Returns resulting string.
    """
    text, _, tlen = strsplit(text, width + 1)
    if tlen > width:
        text, _, _ = strsplit(text, width - 1)

        # Old code always added trailing 'reset' sequence, but strsplit is
        # smarter and only adds it when there is something to reset. However,
        # in order not to distract with changed test data, here's workaround
        # which keeps output exactly the same. TODO: remove it; it doesn't add
        # any practical value for the user.
        if not text.endswith(COLORS['reset']):
            text += COLORS['reset']

        text += wrap_char
    elif pad:
        # The string is short enough, but it might need to be padded.
        text = "%s%*s" % (text, width - tlen, '')
    return text


class Hunk(object):

    def __init__(self, hunk_headers, hunk_meta, old_addr, new_addr):
        self._hunk_headers = hunk_headers
        self._hunk_meta = hunk_meta
        self._old_addr = old_addr   # tuple (start, offset)
        self._new_addr = new_addr   # tuple (start, offset)
        self._hunk_list = []        # list of tuple (attr, line)

    def append(self, hunk_line):
        """hunk_line is a 2-element tuple: (attr, text), where attr is:
                '-': old, '+': new, ' ': common
        """
        self._hunk_list.append(hunk_line)

    def mdiff(self):
        r"""The difflib._mdiff() function returns an interator which returns a
        tuple: (from line tuple, to line tuple, boolean flag)

        from/to line tuple -- (line num, line text)
            line num -- integer or None (to indicate a context separation)
            line text -- original line text with following markers inserted:
                '\0+' -- marks start of added text
                '\0-' -- marks start of deleted text
                '\0^' -- marks start of changed text
                '\1' -- marks end of added/deleted/changed text

        boolean flag -- None indicates context separation, True indicates
            either "from" or "to" line contains a change, otherwise False.
        """
        return difflib._mdiff(self._get_old_text(), self._get_new_text())

    def _get_old_text(self):
        out = []
        for (attr, line) in self._hunk_list:
            if attr != '+':
                out.append(line)
        return out

    def _get_new_text(self):
        out = []
        for (attr, line) in self._hunk_list:
            if attr != '-':
                out.append(line)
        return out

    def is_completed(self):
        old_completed = self._old_addr[1] == len(self._get_old_text())
        new_completed = self._new_addr[1] == len(self._get_new_text())
        return old_completed and new_completed


class UnifiedDiff(object):

    def __init__(self, headers, old_path, new_path, hunks):
        self._headers = headers
        self._old_path = old_path
        self._new_path = new_path
        self._hunks = hunks

    def is_old_path(self, line):
        return line.startswith('--- ')

    def is_new_path(self, line):
        return line.startswith('+++ ')

    def is_hunk_meta(self, line):
        """Minimal valid hunk meta is like '@@ -1 +1 @@', note extra chars
        might occur after the ending @@, e.g. in git log.  '## ' usually
        indicates svn property changes in output from `svn log --diff`
        """
        return (line.startswith('@@ -') and line.find(' @@') >= 8) or \
               (line.startswith('## -') and line.find(' ##') >= 8)

    def parse_hunk_meta(self, hunk_meta):
        # @@ -3,7 +3,6 @@
        a = hunk_meta.split()[1].split(',')   # -3 7
        if len(a) > 1:
            old_addr = (int(a[0][1:]), int(a[1]))
        else:
            # @@ -1 +1,2 @@
            old_addr = (int(a[0][1:]), 1)

        b = hunk_meta.split()[2].split(',')   # +3 6
        if len(b) > 1:
            new_addr = (int(b[0][1:]), int(b[1]))
        else:
            # @@ -0,0 +1 @@
            new_addr = (int(b[0][1:]), 1)

        return (old_addr, new_addr)

    def parse_hunk_line(self, line):
        return (line[0], line[1:])

    def is_old(self, line):
        """Exclude old path and header line from svn log --diff output, allow
        '----' likely to see in diff from yaml file
        """
        return line.startswith('-') and not self.is_old_path(line) and \
            not re.match(r'^-{72}$', line.rstrip())

    def is_new(self, line):
        return line.startswith('+') and not self.is_new_path(line)

    def is_common(self, line):
        return line.startswith(' ')

    def is_eof(self, line):
        # \ No newline at end of file
        # \ No newline at end of property
        return line.startswith(r'\ No newline at end of')

    def is_only_in_dir(self, line):
        return line.startswith('Only in ')

    def is_binary_differ(self, line):
        return re.match('^Binary files .* differ$', line.rstrip())


class PatchStream(object):

    def __init__(self, diff_hdl):
        self._diff_hdl = diff_hdl
        self._stream_header_size = 0
        self._stream_header = []

        # Test whether stream is empty by read 1 line
        line = self._diff_hdl.readline()
        if not line:
            self._is_empty = True
        else:
            self._stream_header.append(line)
            self._stream_header_size += 1
            self._is_empty = False

    def is_empty(self):
        return self._is_empty

    def read_stream_header(self, stream_header_size):
        """Returns a small chunk for patch type detect, suppose to call once"""
        for i in range(1, stream_header_size):
            line = self._diff_hdl.readline()
            if not line:
                break
            self._stream_header.append(line)
            self._stream_header_size += 1
        return self._stream_header

    def __iter__(self):
        for line in self._stream_header:
            yield line
        for line in self._diff_hdl:
            yield line


class PatchStreamForwarder(object):
    """A blocking stream forwarder use `select` and line buffered mode.  Feed
    input stream to a diff format translator and read output stream from it.
    Note input stream is non-seekable, and upstream has eaten some lines.
    """
    def __init__(self, istream, translator):
        assert isinstance(istream, PatchStream)
        assert isinstance(translator, subprocess.Popen)
        self._istream = iter(istream)
        self._in = translator.stdin
        self._out = translator.stdout

    def _can_read(self, timeout=0):
        return select.select([self._out.fileno()], [], [], timeout)[0]

    def _forward_line(self):
        try:
            line = next(self._istream)
            self._in.write(line)
        except StopIteration:
            self._in.close()

    def __iter__(self):
        while True:
            if self._can_read():
                line = self._out.readline()
                if line:
                    yield line
                else:
                    return
            elif not self._in.closed:
                self._forward_line()


class DiffParser(object):

    def __init__(self, stream):

        header = [decode(line) for line in stream.read_stream_header(100)]
        size = len(header)

        if size >= 4 and (header[0].startswith('*** ') and
                          header[1].startswith('--- ') and
                          header[2].rstrip() == '***************' and
                          header[3].startswith('*** ') and
                          header[3].rstrip().endswith(' ****')):
            # For context diff, try use `filterdiff` to translate it to unified
            # format and provide a new stream
            #
            self._type = 'context'
            try:
                # Use line buffered mode so that to readline() in block mode
                self._translator = subprocess.Popen(
                    ['filterdiff', '--format=unified'], stdin=subprocess.PIPE,
                    stdout=subprocess.PIPE, bufsize=1)
            except OSError:
                raise SystemExit('*** Context diff support depends on '
                                 'filterdiff')
            self._stream = PatchStreamForwarder(stream, self._translator)
            return

        for n in range(size):
            if (header[n].startswith('--- ') and (n < size - 1) and
                    header[n + 1].startswith('+++ ')):
                self._type = 'unified'
                self._stream = stream
                break
        else:
            # `filterdiff` translates unknown diff to nothing, fall through to
            # unified diff give cdiff a chance to show everything as headers
            #
            sys.stderr.write("*** unknown format, fall through to 'unified'\n")
            self._type = 'unified'
            self._stream = stream

    def get_diff_generator(self):
        """parse all diff lines, construct a list of UnifiedDiff objects"""
        diff = UnifiedDiff([], None, None, [])
        headers = []

        for line in self._stream:
            line = decode(line)

            if diff.is_old_path(line):
                # This is a new diff when current hunk is not yet genreated or
                # is completed.  We yield previous diff if exists and construct
                # a new one for this case.  Otherwise it's acutally an 'old'
                # line starts with '--- '.
                #
                if (not diff._hunks or diff._hunks[-1].is_completed()):
                    if diff._old_path and diff._new_path and diff._hunks:
                        yield diff
                    diff = UnifiedDiff(headers, line, None, [])
                    headers = []
                else:
                    diff._hunks[-1].append(diff.parse_hunk_line(line))

            elif diff.is_new_path(line) and diff._old_path:
                if not diff._new_path:
                    diff._new_path = line
                else:
                    diff._hunks[-1].append(diff.parse_hunk_line(line))

            elif diff.is_hunk_meta(line):
                hunk_meta = line
                try:
                    old_addr, new_addr = diff.parse_hunk_meta(hunk_meta)
                except (IndexError, ValueError):
                    raise RuntimeError('invalid hunk meta: %s' % hunk_meta)
                hunk = Hunk(headers, hunk_meta, old_addr, new_addr)
                headers = []
                diff._hunks.append(hunk)

            elif diff._hunks and not headers and (diff.is_old(line) or
                                                  diff.is_new(line) or
                                                  diff.is_common(line)):
                diff._hunks[-1].append(diff.parse_hunk_line(line))

            elif diff.is_eof(line):
                # ignore
                pass

            elif diff.is_only_in_dir(line) or \
                    diff.is_binary_differ(line):
                # 'Only in foo:' and 'Binary files ... differ' are considered
                # as separate diffs, so yield current diff, then this line
                #
                if diff._old_path and diff._new_path and diff._hunks:
                    # Current diff is comppletely constructed
                    yield diff
                headers.append(line)
                yield UnifiedDiff(headers, '', '', [])
                headers = []
                diff = UnifiedDiff([], None, None, [])

            else:
                # All other non-recognized lines are considered as headers or
                # hunk headers respectively
                #
                headers.append(line)

        # Validate and yield the last patch set if it is not yielded yet
        if diff._old_path:
            assert diff._new_path is not None
            if diff._hunks:
                assert len(diff._hunks[-1]._hunk_meta) > 0
                assert len(diff._hunks[-1]._hunk_list) > 0
            yield diff

        if headers:
            # Tolerate dangling headers, just yield a UnifiedDiff object with
            # only header lines
            #
            yield UnifiedDiff(headers, '', '', [])


class DiffMarker(object):

    def markup(self, diffs, side_by_side=False, width=0, tab_width=8,
               wrap=False):
        """Returns a generator"""
        if side_by_side:
            for diff in diffs:
                for line in self._markup_side_by_side(diff, width, tab_width,
                                                      wrap):
                    yield line
        else:
            for diff in diffs:
                for line in self._markup_traditional(diff):
                    yield line

    def _markup_traditional(self, diff):
        """Returns a generator"""
        for line in diff._headers:
            yield self._markup_header(line)

        yield self._markup_old_path(diff._old_path)
        yield self._markup_new_path(diff._new_path)

        for hunk in diff._hunks:
            for hunk_header in hunk._hunk_headers:
                yield self._markup_hunk_header(hunk_header)
            yield self._markup_hunk_meta(hunk._hunk_meta)
            for old, new, changed in hunk.mdiff():
                if changed:
                    if not old[0]:
                        # The '+' char after \x00 is kept
                        # DEBUG: yield 'NEW: %s %s\n' % (old, new)
                        line = new[1].strip('\x00\x01')
                        yield self._markup_new(line)
                    elif not new[0]:
                        # The '-' char after \x00 is kept
                        # DEBUG: yield 'OLD: %s %s\n' % (old, new)
                        line = old[1].strip('\x00\x01')
                        yield self._markup_old(line)
                    else:
                        # DEBUG: yield 'CHG: %s %s\n' % (old, new)
                        yield self._markup_old('-') + \
                            self._markup_mix(old[1], 'red')
                        yield self._markup_new('+') + \
                            self._markup_mix(new[1], 'green')
                else:
                    yield self._markup_common(' ' + old[1])

    def _markup_side_by_side(self, diff, width, tab_width, wrap):
        """Returns a generator"""

        def _normalize(line):
            return line.replace(
                '\t', ' ' * tab_width).replace('\n', '').replace('\r', '')

        def _fit_with_marker_mix(text, base_color, width):
            """Wrap input text which contains mdiff tags, markup at the
            meantime
            """
            out = [COLORS[base_color]]
            tag_re = re.compile(r'\x00[+^-]|\x01')

            while text:
                if text.startswith('\x00-'):    # del
                    out.append(COLORS['reverse'] + COLORS[base_color])
                    text = text[2:]
                elif text.startswith('\x00+'):  # add
                    out.append(COLORS['reverse'] + COLORS[base_color])
                    text = text[2:]
                elif text.startswith('\x00^'):  # change
                    out.append(COLORS['underline'] + COLORS[base_color])
                    text = text[2:]
                elif text.startswith('\x01'):   # reset
                    # TODO: Append resetting sequence if only there is some
                    # text after that. That is, call out.append(...) if only
                    # len(text) > 1.
                    out.append(COLORS['reset'] + COLORS[base_color])
                    text = text[1:]
                else:
                    # FIXME: utf-8 wchar might break the rule here, e.g.
                    # u'\u554a' takes double width of a single letter, also
                    # this depends on your terminal font.  I guess audience of
                    # this tool never put that kind of symbol in their code :-)
                    #
                    out.append(text[0])
                    text = text[1:]

            out.append(COLORS['reset'])

            return ''.join(out)

        # Set up number width, note last hunk might be empty
        try:
            (start, offset) = diff._hunks[-1]._old_addr
            max1 = start + offset - 1
            (start, offset) = diff._hunks[-1]._new_addr
            max2 = start + offset - 1
        except IndexError:
            max1 = max2 = 0
        num_width = max(len(str(max1)), len(str(max2)))

        # Set up line width
        if width <= 0:
            # Autodetection of text width according to terminal size
            try:
                # Each line is like "nnn TEXT nnn TEXT\n", so width is half of
                # [terminal size minus the line number columns and 3 separating
                # spaces
                #
                width = (terminal_size()[0] - num_width * 2 - 3) // 2
            except Exception:
                # If terminal detection failed, set back to default
                width = 80

        # Setup lineno and line format
        left_num_fmt = colorize('%%(left_num)%ds' % num_width, 'yellow')
        right_num_fmt = colorize('%%(right_num)%ds' % num_width, 'yellow')
        line_fmt = left_num_fmt + ' %(left)s ' + COLORS['reset'] + \
            right_num_fmt + ' %(right)s\n'

        # yield header, old path and new path
        for line in diff._headers:
            yield self._markup_header(line)
        yield self._markup_old_path(diff._old_path)
        yield self._markup_new_path(diff._new_path)

        # yield hunks
        for hunk in diff._hunks:
            for hunk_header in hunk._hunk_headers:
                yield self._markup_hunk_header(hunk_header)
            yield self._markup_hunk_meta(hunk._hunk_meta)
            for old, new, changed in hunk.mdiff():
                if old[0]:
                    left_num = str(hunk._old_addr[0] + int(old[0]) - 1)
                else:
                    left_num = ' '

                if new[0]:
                    right_num = str(hunk._new_addr[0] + int(new[0]) - 1)
                else:
                    right_num = ' '

                left = _normalize(old[1])
                right = _normalize(new[1])

                if changed:
                    if not old[0]:
                        left = ''
                        right = right.rstrip('\x01')
                        if right.startswith('\x00+'):
                            right = right[2:]
                        right = self._markup_new(right)
                    elif not new[0]:
                        left = left.rstrip('\x01')
                        if left.startswith('\x00-'):
                            left = left[2:]
                        left = self._markup_old(left)
                        right = ''
                    else:
                        left = _fit_with_marker_mix(left, 'red', width)
                        right = _fit_with_marker_mix(right, 'green', width)
                else:
                    left = self._markup_common(left)
                    right = self._markup_common(right)

                if wrap:
                    # Need to wrap long lines, so here we'll iterate,
                    # shaving off `width` chars from both left and right
                    # strings, until both are empty. Also, line number needs to
                    # be printed only for the first part.
                    lncur = left_num
                    rncur = right_num
                    while len(left) > 0 or len(right) > 0:
                        # Split both left and right lines, preserving escaping
                        # sequences correctly.
                        lcur, left, llen = strsplit(left, width)
                        rcur, right, rlen = strsplit(right, width)

                        # Pad left line with spaces if needed
                        if llen < width:
                            lcur = "%s%*s" % (lcur, width - llen, '')

                        yield line_fmt % {
                            'left_num': lncur,
                            'left': lcur,
                            'right_num': rncur,
                            'right': rcur
                        }

                        # Clean line numbers for further iterations
                        lncur = ''
                        rncur = ''
                else:
                    # Don't need to wrap long lines; instead, a trailing '>'
                    # char needs to be appended.
                    wrap_char = colorize('>', 'lightmagenta')
                    left = strtrim(left, width, wrap_char, len(right) > 0)
                    right = strtrim(right, width, wrap_char, False)

                    yield line_fmt % {
                        'left_num': left_num,
                        'left': left,
                        'right_num': right_num,
                        'right': right
                    }

    def _markup_header(self, line):
        return colorize(line, 'cyan')

    def _markup_old_path(self, line):
        return colorize(line, 'yellow')

    def _markup_new_path(self, line):
        return colorize(line, 'yellow')

    def _markup_hunk_header(self, line):
        return colorize(line, 'lightcyan')

    def _markup_hunk_meta(self, line):
        return colorize(line, 'lightblue')

    def _markup_common(self, line):
        return colorize(line, 'reset')

    def _markup_old(self, line):
        return colorize(line, 'lightred')

    def _markup_new(self, line):
        return colorize(line, 'green')

    def _markup_mix(self, line, base_color):
        del_code = COLORS['reverse'] + COLORS[base_color]
        add_code = COLORS['reverse'] + COLORS[base_color]
        chg_code = COLORS['underline'] + COLORS[base_color]
        rst_code = COLORS['reset'] + COLORS[base_color]
        line = line.replace('\x00-', del_code)
        line = line.replace('\x00+', add_code)
        line = line.replace('\x00^', chg_code)
        line = line.replace('\x01', rst_code)
        return colorize(line, base_color)


def markup_to_pager(stream, opts):
    """Pipe unified diff stream to pager (less).

    Note: have to create pager Popen object before the translator Popen object
    in PatchStreamForwarder, otherwise the `stdin=subprocess.PIPE` would cause
    trouble to the translator pipe (select() never see EOF after input stream
    ended), most likely python bug 12607 (http://bugs.python.org/issue12607)
    which was fixed in python 2.7.3.

    See issue #30 (https://github.com/ymattw/cdiff/issues/30) for more
    information.
    """
    pager_cmd = ['less']
    if not os.getenv('LESS'):
        # Args stolen from git source: github.com/git/git/blob/master/pager.c
        pager_cmd.extend(['-FRSX', '--shift 1'])
    pager = subprocess.Popen(
        pager_cmd, stdin=subprocess.PIPE, stdout=sys.stdout)

    diffs = DiffParser(stream).get_diff_generator()
    marker = DiffMarker()
    color_diff = marker.markup(diffs, side_by_side=opts.side_by_side,
                               width=opts.width, tab_width=opts.tab_width,
                               wrap=opts.wrap)

    for line in color_diff:
        pager.stdin.write(line.encode('utf-8'))

    pager.stdin.close()
    pager.wait()


def check_command_status(arguments):
    """Return True if command returns 0."""
    try:
        return subprocess.call(
            arguments, stdout=subprocess.PIPE, stderr=subprocess.PIPE) == 0
    except OSError:
        return False


def revision_control_diff(args):
    """Return diff from revision control system."""
    for _, ops in VCS_INFO.items():
        if check_command_status(ops['probe']):
            return subprocess.Popen(
                ops['diff'] + args, stdout=subprocess.PIPE).stdout


def revision_control_log(args):
    """Return log from revision control system."""
    for _, ops in VCS_INFO.items():
        if check_command_status(ops['probe']):
            return subprocess.Popen(
                ops['log'] + args, stdout=subprocess.PIPE).stdout


def decode(line):
    """Decode UTF-8 if necessary."""
    if isinstance(line, unicode):
        return line

    for encoding in ['utf-8', 'latin1']:
        try:
            return line.decode(encoding)
        except UnicodeDecodeError:
            pass

    return '*** cdiff: undecodable bytes ***\n'


def terminal_size():
    """Returns terminal size. Taken from https://gist.github.com/marsam/7268750
    but removed win32 support which depends on 3rd party extension.
    """
    width, height = None, None
    try:
        import struct
        import fcntl
        import termios
        s = struct.pack('HHHH', 0, 0, 0, 0)
        x = fcntl.ioctl(1, termios.TIOCGWINSZ, s)
        height, width = struct.unpack('HHHH', x)[0:2]
    except (IOError, AttributeError):
        pass
    return width, height


def main():
    signal.signal(signal.SIGPIPE, signal.SIG_DFL)
    signal.signal(signal.SIGINT, signal.SIG_DFL)

    from optparse import (OptionParser, BadOptionError, AmbiguousOptionError,
                          OptionGroup)

    class PassThroughOptionParser(OptionParser):
        """Stop parsing on first unknown option (e.g. --cached, -U10) and pass
        them down.  Note the `opt_str` in exception object does not give us
        chance to take the full option back, e.g. for '-U10' it will only
        contain '-U' and the '10' part will be lost.  Ref: http://goo.gl/IqY4A
        (on stackoverflow).  My hack is to try parse and insert a '--' in place
        and parse again.  Let me know if someone has better solution.
        """
        def _process_args(self, largs, rargs, values):
            left = largs[:]
            right = rargs[:]
            try:
                OptionParser._process_args(self, left, right, values)
            except (BadOptionError, AmbiguousOptionError):
                parsed_num = len(rargs) - len(right) - 1
                rargs.insert(parsed_num, '--')
            OptionParser._process_args(self, largs, rargs, values)

    supported_vcs = sorted(VCS_INFO.keys())

    usage = """%prog [options] [file|dir ...]"""
    parser = PassThroughOptionParser(
        usage=usage, description=META_INFO['description'],
        version='%%prog %s' % META_INFO['version'])
    parser.add_option(
        '-s', '--side-by-side', action='store_true',
        help='enable side-by-side mode')
    parser.add_option(
        '-w', '--width', type='int', default=80, metavar='N',
        help='set text width for side-by-side mode, 0 for auto detection, '
             'default is 80')
    parser.add_option(
        '-l', '--log', action='store_true',
        help='show log with changes from revision control')
    parser.add_option(
        '-c', '--color', default='auto', metavar='M',
        help="""colorize mode 'auto' (default), 'always', or 'never'""")
    parser.add_option(
        '-t', '--tab-width', type='int', default=8, metavar='N',
        help="""convert tab characters to this many spcaes (default: 8)""")
    parser.add_option(
        '', '--wrap', action='store_true',
        help='wrap long lines in side-by-side view')

    # Hack: use OptionGroup text for extra help message after option list
    option_group = OptionGroup(
        parser, "Note", ("Option parser will stop on first unknown option "
                         "and pass them down to underneath revision control. "
                         "Environment variable CDIFF_OPTIONS may be used to "
                         "specify default options that will be placed at the "
                         "beginning of the argument list."))
    parser.add_option_group(option_group)

    # Place possible options defined in CDIFF_OPTIONS at the beginning of argv
    cdiff_opts = [x for x in os.getenv('CDIFF_OPTIONS', '').split(' ') if x]
    opts, args = parser.parse_args(cdiff_opts + sys.argv[1:])

    if opts.log:
        diff_hdl = revision_control_log(args)
        if not diff_hdl:
            sys.stderr.write(('*** Not in a supported workspace, supported '
                              'are: %s\n') % ', '.join(supported_vcs))
            return 1
    elif sys.stdin.isatty():
        diff_hdl = revision_control_diff(args)
        if not diff_hdl:
            sys.stderr.write(('*** Not in a supported workspace, supported '
                              'are: %s\n\n') % ', '.join(supported_vcs))
            parser.print_help()
            return 1
    else:
        diff_hdl = (sys.stdin.buffer if hasattr(sys.stdin, 'buffer')
                    else sys.stdin)

    stream = PatchStream(diff_hdl)

    # Don't let empty diff pass thru
    if stream.is_empty():
        return 0

    if opts.color == 'always' or \
            (opts.color == 'auto' and sys.stdout.isatty()):
        markup_to_pager(stream, opts)
    else:
        # pipe out stream untouched to make sure it is still a patch
        byte_output = (sys.stdout.buffer if hasattr(sys.stdout, 'buffer')
                       else sys.stdout)
        for line in stream:
            byte_output.write(line)

    if diff_hdl is not sys.stdin:
        diff_hdl.close()

    return 0


if __name__ == '__main__':
    sys.exit(main())

# vim:set et sts=4 sw=4 tw=79: