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]


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):
        """Returns a generator"""
        if side_by_side:
            for diff in diffs:
                for line in self._markup_side_by_side(diff, width, tab_width):
                    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):
        """Returns a generator"""
        wrap_char = colorize('>', 'lightmagenta')

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

        def _fit_with_marker(text, markup_fn, width, pad=False):
            """Wrap or pad input pure text, then markup"""
            if len(text) > width:
                return markup_fn(text[:(width - 1)]) + wrap_char
            elif pad:
                pad_len = width - len(text)
                return '%s%*s' % (markup_fn(text), pad_len, '')
            else:
                return markup_fn(text)

        def _fit_with_marker_mix(text, base_color, width, pad=False):
            """Wrap or pad input text which contains mdiff tags, markup at the
            meantime, note only left side need to set `pad`
            """
            out = [COLORS[base_color]]
            count = 0
            tag_re = re.compile(r'\x00[+^-]|\x01')

            while text and count < width:
                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
                    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])
                    count += 1
                    text = text[1:]

            if count == width and tag_re.sub('', text):
                # Was stripped: output fulfil and still has normal char in text
                out[-1] = COLORS['reset'] + wrap_char
            elif count < width and pad:
                pad_len = width - count
                out.append('%s%*s' % (COLORS['reset'], pad_len, ''))
            else:
                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 = '%*s' % (width, ' ')
                        right = right.rstrip('\x01')
                        if right.startswith('\x00+'):
                            right = right[2:]
                        right = _fit_with_marker(
                            right, self._markup_new, width)
                    elif not new[0]:
                        left = left.rstrip('\x01')
                        if left.startswith('\x00-'):
                            left = left[2:]
                        left = _fit_with_marker(left, self._markup_old, width)
                        right = ''
                    else:
                        left = _fit_with_marker_mix(left, 'red', width, 1)
                        right = _fit_with_marker_mix(right, 'green', width)
                else:
                    left = _fit_with_marker(
                        left, self._markup_common, width, 1)
                    right = _fit_with_marker(right, self._markup_common, width)
                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)

    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)""")

    # 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: