tests/hghave.py

copies: detect case when a merge decision overwrite previous data

We now detect and record when a merge case required special logic (eg: thing
that append during the merge, ambiguity leading to picking p1 data, etc) and we
explicitly mark the result as superseding the previous data.

This fixes the family of test we previously added.

Differential Revision: https://phab.mercurial-scm.org/D9613

from __future__ import absolute_import, print_function

import distutils.version
import os
import re
import socket
import stat
import subprocess
import sys
import tempfile

tempprefix = 'hg-hghave-'

checks = {
    "true": (lambda: True, "yak shaving"),
    "false": (lambda: False, "nail clipper"),
    "known-bad-output": (lambda: True, "use for currently known bad output"),
    "missing-correct-output": (lambda: False, "use for missing good output"),
}

try:
    import msvcrt

    msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
    msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY)
except ImportError:
    pass

stdout = getattr(sys.stdout, 'buffer', sys.stdout)
stderr = getattr(sys.stderr, 'buffer', sys.stderr)

if sys.version_info[0] >= 3:

    def _sys2bytes(p):
        if p is None:
            return p
        return p.encode('utf-8')

    def _bytes2sys(p):
        if p is None:
            return p
        return p.decode('utf-8')


else:

    def _sys2bytes(p):
        return p

    _bytes2sys = _sys2bytes


def check(name, desc):
    """Registers a check function for a feature."""

    def decorator(func):
        checks[name] = (func, desc)
        return func

    return decorator


def checkvers(name, desc, vers):
    """Registers a check function for each of a series of versions.

    vers can be a list or an iterator.

    Produces a series of feature checks that have the form <name><vers> without
    any punctuation (even if there's punctuation in 'vers'; i.e. this produces
    'py38', not 'py3.8' or 'py-38')."""

    def decorator(func):
        def funcv(v):
            def f():
                return func(v)

            return f

        for v in vers:
            v = str(v)
            f = funcv(v)
            checks['%s%s' % (name, v.replace('.', ''))] = (f, desc % v)
        return func

    return decorator


def checkfeatures(features):
    result = {
        'error': [],
        'missing': [],
        'skipped': [],
    }

    for feature in features:
        negate = feature.startswith('no-')
        if negate:
            feature = feature[3:]

        if feature not in checks:
            result['missing'].append(feature)
            continue

        check, desc = checks[feature]
        try:
            available = check()
        except Exception:
            result['error'].append('hghave check failed: %s' % feature)
            continue

        if not negate and not available:
            result['skipped'].append('missing feature: %s' % desc)
        elif negate and available:
            result['skipped'].append('system supports %s' % desc)

    return result


def require(features):
    """Require that features are available, exiting if not."""
    result = checkfeatures(features)

    for missing in result['missing']:
        stderr.write(
            ('skipped: unknown feature: %s\n' % missing).encode('utf-8')
        )
    for msg in result['skipped']:
        stderr.write(('skipped: %s\n' % msg).encode('utf-8'))
    for msg in result['error']:
        stderr.write(('%s\n' % msg).encode('utf-8'))

    if result['missing']:
        sys.exit(2)

    if result['skipped'] or result['error']:
        sys.exit(1)


def matchoutput(cmd, regexp, ignorestatus=False):
    """Return the match object if cmd executes successfully and its output
    is matched by the supplied regular expression.
    """
    r = re.compile(regexp)
    p = subprocess.Popen(
        cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT
    )
    s = p.communicate()[0]
    ret = p.returncode
    return (ignorestatus or not ret) and r.search(s)


@check("baz", "GNU Arch baz client")
def has_baz():
    return matchoutput('baz --version 2>&1', br'baz Bazaar version')


@check("bzr", "Canonical's Bazaar client")
def has_bzr():
    try:
        import bzrlib
        import bzrlib.bzrdir
        import bzrlib.errors
        import bzrlib.revision
        import bzrlib.revisionspec

        bzrlib.revisionspec.RevisionSpec
        return bzrlib.__doc__ is not None
    except (AttributeError, ImportError):
        return False


@checkvers("bzr", "Canonical's Bazaar client >= %s", (1.14,))
def has_bzr_range(v):
    major, minor = v.split('rc')[0].split('.')[0:2]
    try:
        import bzrlib

        return bzrlib.__doc__ is not None and bzrlib.version_info[:2] >= (
            int(major),
            int(minor),
        )
    except ImportError:
        return False


@check("chg", "running with chg")
def has_chg():
    return 'CHGHG' in os.environ


@check("cvs", "cvs client/server")
def has_cvs():
    re = br'Concurrent Versions System.*?server'
    return matchoutput('cvs --version 2>&1', re) and not has_msys()


@check("cvs112", "cvs client/server 1.12.* (not cvsnt)")
def has_cvs112():
    re = br'Concurrent Versions System \(CVS\) 1.12.*?server'
    return matchoutput('cvs --version 2>&1', re) and not has_msys()


@check("cvsnt", "cvsnt client/server")
def has_cvsnt():
    re = br'Concurrent Versions System \(CVSNT\) (\d+).(\d+).*\(client/server\)'
    return matchoutput('cvsnt --version 2>&1', re)


@check("darcs", "darcs client")
def has_darcs():
    return matchoutput('darcs --version', br'\b2\.([2-9]|\d{2})', True)


@check("mtn", "monotone client (>= 1.0)")
def has_mtn():
    return matchoutput('mtn --version', br'monotone', True) and not matchoutput(
        'mtn --version', br'monotone 0\.', True
    )


@check("eol-in-paths", "end-of-lines in paths")
def has_eol_in_paths():
    try:
        fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix, suffix='\n\r')
        os.close(fd)
        os.remove(path)
        return True
    except (IOError, OSError):
        return False


@check("execbit", "executable bit")
def has_executablebit():
    try:
        EXECFLAGS = stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
        fh, fn = tempfile.mkstemp(dir='.', prefix=tempprefix)
        try:
            os.close(fh)
            m = os.stat(fn).st_mode & 0o777
            new_file_has_exec = m & EXECFLAGS
            os.chmod(fn, m ^ EXECFLAGS)
            exec_flags_cannot_flip = (os.stat(fn).st_mode & 0o777) == m
        finally:
            os.unlink(fn)
    except (IOError, OSError):
        # we don't care, the user probably won't be able to commit anyway
        return False
    return not (new_file_has_exec or exec_flags_cannot_flip)


@check("icasefs", "case insensitive file system")
def has_icasefs():
    # Stolen from mercurial.util
    fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix)
    os.close(fd)
    try:
        s1 = os.stat(path)
        d, b = os.path.split(path)
        p2 = os.path.join(d, b.upper())
        if path == p2:
            p2 = os.path.join(d, b.lower())
        try:
            s2 = os.stat(p2)
            return s2 == s1
        except OSError:
            return False
    finally:
        os.remove(path)


@check("fifo", "named pipes")
def has_fifo():
    if getattr(os, "mkfifo", None) is None:
        return False
    name = tempfile.mktemp(dir='.', prefix=tempprefix)
    try:
        os.mkfifo(name)
        os.unlink(name)
        return True
    except OSError:
        return False


@check("killdaemons", 'killdaemons.py support')
def has_killdaemons():
    return True


@check("cacheable", "cacheable filesystem")
def has_cacheable_fs():
    from mercurial import util

    fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix)
    os.close(fd)
    try:
        return util.cachestat(path).cacheable()
    finally:
        os.remove(path)


@check("lsprof", "python lsprof module")
def has_lsprof():
    try:
        import _lsprof

        _lsprof.Profiler  # silence unused import warning
        return True
    except ImportError:
        return False


def _gethgversion():
    m = matchoutput('hg --version --quiet 2>&1', br'(\d+)\.(\d+)')
    if not m:
        return (0, 0)
    return (int(m.group(1)), int(m.group(2)))


_hgversion = None


def gethgversion():
    global _hgversion
    if _hgversion is None:
        _hgversion = _gethgversion()
    return _hgversion


@checkvers(
    "hg", "Mercurial >= %s", list([(1.0 * x) / 10 for x in range(9, 99)])
)
def has_hg_range(v):
    major, minor = v.split('.')[0:2]
    return gethgversion() >= (int(major), int(minor))


@check("rust", "Using the Rust extensions")
def has_rust():
    """Check is the mercurial currently running is using some rust code"""
    cmd = 'hg debuginstall --quiet 2>&1'
    match = br'checking module policy \(([^)]+)\)'
    policy = matchoutput(cmd, match)
    if not policy:
        return False
    return b'rust' in policy.group(1)


@check("hg08", "Mercurial >= 0.8")
def has_hg08():
    if checks["hg09"][0]():
        return True
    return matchoutput('hg help annotate 2>&1', '--date')


@check("hg07", "Mercurial >= 0.7")
def has_hg07():
    if checks["hg08"][0]():
        return True
    return matchoutput('hg --version --quiet 2>&1', 'Mercurial Distributed SCM')


@check("hg06", "Mercurial >= 0.6")
def has_hg06():
    if checks["hg07"][0]():
        return True
    return matchoutput('hg --version --quiet 2>&1', 'Mercurial version')


@check("gettext", "GNU Gettext (msgfmt)")
def has_gettext():
    return matchoutput('msgfmt --version', br'GNU gettext-tools')


@check("git", "git command line client")
def has_git():
    return matchoutput('git --version 2>&1', br'^git version')


def getgitversion():
    m = matchoutput('git --version 2>&1', br'git version (\d+)\.(\d+)')
    if not m:
        return (0, 0)
    return (int(m.group(1)), int(m.group(2)))


@check("pygit2", "pygit2 Python library")
def has_git():
    try:
        import pygit2

        pygit2.Oid  # silence unused import
        return True
    except ImportError:
        return False


# https://github.com/git-lfs/lfs-test-server
@check("lfs-test-server", "git-lfs test server")
def has_lfsserver():
    exe = 'lfs-test-server'
    if has_windows():
        exe = 'lfs-test-server.exe'
    return any(
        os.access(os.path.join(path, exe), os.X_OK)
        for path in os.environ["PATH"].split(os.pathsep)
    )


@checkvers("git", "git client (with ext::sh support) version >= %s", (1.9,))
def has_git_range(v):
    major, minor = v.split('.')[0:2]
    return getgitversion() >= (int(major), int(minor))


@check("docutils", "Docutils text processing library")
def has_docutils():
    try:
        import docutils.core

        docutils.core.publish_cmdline  # silence unused import
        return True
    except ImportError:
        return False


def getsvnversion():
    m = matchoutput('svn --version --quiet 2>&1', br'^(\d+)\.(\d+)')
    if not m:
        return (0, 0)
    return (int(m.group(1)), int(m.group(2)))


@checkvers("svn", "subversion client and admin tools >= %s", (1.3, 1.5))
def has_svn_range(v):
    major, minor = v.split('.')[0:2]
    return getsvnversion() >= (int(major), int(minor))


@check("svn", "subversion client and admin tools")
def has_svn():
    return matchoutput('svn --version 2>&1', br'^svn, version') and matchoutput(
        'svnadmin --version 2>&1', br'^svnadmin, version'
    )


@check("svn-bindings", "subversion python bindings")
def has_svn_bindings():
    try:
        import svn.core

        version = svn.core.SVN_VER_MAJOR, svn.core.SVN_VER_MINOR
        if version < (1, 4):
            return False
        return True
    except ImportError:
        return False


@check("p4", "Perforce server and client")
def has_p4():
    return matchoutput('p4 -V', br'Rev\. P4/') and matchoutput(
        'p4d -V', br'Rev\. P4D/'
    )


@check("symlink", "symbolic links")
def has_symlink():
    # mercurial.windows.checklink() is a hard 'no' at the moment
    if os.name == 'nt' or getattr(os, "symlink", None) is None:
        return False
    name = tempfile.mktemp(dir='.', prefix=tempprefix)
    try:
        os.symlink(".", name)
        os.unlink(name)
        return True
    except (OSError, AttributeError):
        return False


@check("hardlink", "hardlinks")
def has_hardlink():
    from mercurial import util

    fh, fn = tempfile.mkstemp(dir='.', prefix=tempprefix)
    os.close(fh)
    name = tempfile.mktemp(dir='.', prefix=tempprefix)
    try:
        util.oslink(_sys2bytes(fn), _sys2bytes(name))
        os.unlink(name)
        return True
    except OSError:
        return False
    finally:
        os.unlink(fn)


@check("hardlink-whitelisted", "hardlinks on whitelisted filesystems")
def has_hardlink_whitelisted():
    from mercurial import util

    try:
        fstype = util.getfstype(b'.')
    except OSError:
        return False
    return fstype in util._hardlinkfswhitelist


@check("rmcwd", "can remove current working directory")
def has_rmcwd():
    ocwd = os.getcwd()
    temp = tempfile.mkdtemp(dir='.', prefix=tempprefix)
    try:
        os.chdir(temp)
        # On Linux, 'rmdir .' isn't allowed, but the other names are okay.
        # On Solaris and Windows, the cwd can't be removed by any names.
        os.rmdir(os.getcwd())
        return True
    except OSError:
        return False
    finally:
        os.chdir(ocwd)
        # clean up temp dir on platforms where cwd can't be removed
        try:
            os.rmdir(temp)
        except OSError:
            pass


@check("tla", "GNU Arch tla client")
def has_tla():
    return matchoutput('tla --version 2>&1', br'The GNU Arch Revision')


@check("gpg", "gpg client")
def has_gpg():
    return matchoutput('gpg --version 2>&1', br'GnuPG')


@check("gpg2", "gpg client v2")
def has_gpg2():
    return matchoutput('gpg --version 2>&1', br'GnuPG[^0-9]+2\.')


@check("gpg21", "gpg client v2.1+")
def has_gpg21():
    return matchoutput('gpg --version 2>&1', br'GnuPG[^0-9]+2\.(?!0)')


@check("unix-permissions", "unix-style permissions")
def has_unix_permissions():
    d = tempfile.mkdtemp(dir='.', prefix=tempprefix)
    try:
        fname = os.path.join(d, 'foo')
        for umask in (0o77, 0o07, 0o22):
            os.umask(umask)
            f = open(fname, 'w')
            f.close()
            mode = os.stat(fname).st_mode
            os.unlink(fname)
            if mode & 0o777 != ~umask & 0o666:
                return False
        return True
    finally:
        os.rmdir(d)


@check("unix-socket", "AF_UNIX socket family")
def has_unix_socket():
    return getattr(socket, 'AF_UNIX', None) is not None


@check("root", "root permissions")
def has_root():
    return getattr(os, 'geteuid', None) and os.geteuid() == 0


@check("pyflakes", "Pyflakes python linter")
def has_pyflakes():
    try:
        import pyflakes

        pyflakes.__version__
    except ImportError:
        return False
    else:
        return True


@check("pylint", "Pylint python linter")
def has_pylint():
    return matchoutput("pylint --help", br"Usage:[ ]+pylint", True)


@check("clang-format", "clang-format C code formatter (>= 11)")
def has_clang_format():
    m = matchoutput('clang-format --version', br'clang-format version (\d+)')
    # style changed somewhere between 10.x and 11.x
    return m and int(m.group(1)) >= 11


@check("jshint", "JSHint static code analysis tool")
def has_jshint():
    return matchoutput("jshint --version 2>&1", br"jshint v")


@check("pygments", "Pygments source highlighting library")
def has_pygments():
    try:
        import pygments

        pygments.highlight  # silence unused import warning
        return True
    except ImportError:
        return False


@check("pygments25", "Pygments version >= 2.5")
def pygments25():
    try:
        import pygments

        v = pygments.__version__
    except ImportError:
        return False

    parts = v.split(".")
    major = int(parts[0])
    minor = int(parts[1])

    return (major, minor) >= (2, 5)


@check("outer-repo", "outer repo")
def has_outer_repo():
    # failing for other reasons than 'no repo' imply that there is a repo
    return not matchoutput('hg root 2>&1', br'abort: no repository found', True)


@check("ssl", "ssl module available")
def has_ssl():
    try:
        import ssl

        ssl.CERT_NONE
        return True
    except ImportError:
        return False


@check("defaultcacertsloaded", "detected presence of loaded system CA certs")
def has_defaultcacertsloaded():
    import ssl
    from mercurial import sslutil, ui as uimod

    ui = uimod.ui.load()
    cafile = sslutil._defaultcacerts(ui)
    ctx = ssl.create_default_context()
    if cafile:
        ctx.load_verify_locations(cafile=cafile)
    else:
        ctx.load_default_certs()

    return len(ctx.get_ca_certs()) > 0


@check("tls1.2", "TLS 1.2 protocol support")
def has_tls1_2():
    from mercurial import sslutil

    return b'tls1.2' in sslutil.supportedprotocols


@check("windows", "Windows")
def has_windows():
    return os.name == 'nt'


@check("system-sh", "system() uses sh")
def has_system_sh():
    return os.name != 'nt'


@check("serve", "platform and python can manage 'hg serve -d'")
def has_serve():
    return True


@check("setprocname", "whether osutil.setprocname is available or not")
def has_setprocname():
    try:
        from mercurial.utils import procutil

        procutil.setprocname
        return True
    except AttributeError:
        return False


@check("test-repo", "running tests from repository")
def has_test_repo():
    t = os.environ["TESTDIR"]
    return os.path.isdir(os.path.join(t, "..", ".hg"))


@check("curses", "terminfo compiler and curses module")
def has_curses():
    try:
        import curses

        curses.COLOR_BLUE

        # Windows doesn't have a `tic` executable, but the windows_curses
        # package is sufficient to run the tests without it.
        if os.name == 'nt':
            return True

        return has_tic()

    except (ImportError, AttributeError):
        return False


@check("tic", "terminfo compiler")
def has_tic():
    return matchoutput('test -x "`which tic`"', br'')


@check("xz", "xz compression utility")
def has_xz():
    # When Windows invokes a subprocess in shell mode, it uses `cmd.exe`, which
    # only knows `where`, not `which`.  So invoke MSYS shell explicitly.
    return matchoutput("sh -c 'test -x \"`which xz`\"'", b'')


@check("msys", "Windows with MSYS")
def has_msys():
    return os.getenv('MSYSTEM')


@check("aix", "AIX")
def has_aix():
    return sys.platform.startswith("aix")


@check("osx", "OS X")
def has_osx():
    return sys.platform == 'darwin'


@check("osxpackaging", "OS X packaging tools")
def has_osxpackaging():
    try:
        return (
            matchoutput('pkgbuild', br'Usage: pkgbuild ', ignorestatus=1)
            and matchoutput(
                'productbuild', br'Usage: productbuild ', ignorestatus=1
            )
            and matchoutput('lsbom', br'Usage: lsbom', ignorestatus=1)
            and matchoutput('xar --help', br'Usage: xar', ignorestatus=1)
        )
    except ImportError:
        return False


@check('linuxormacos', 'Linux or MacOS')
def has_linuxormacos():
    # This isn't a perfect test for MacOS. But it is sufficient for our needs.
    return sys.platform.startswith(('linux', 'darwin'))


@check("docker", "docker support")
def has_docker():
    pat = br'A self-sufficient runtime for'
    if matchoutput('docker --help', pat):
        if 'linux' not in sys.platform:
            # TODO: in theory we should be able to test docker-based
            # package creation on non-linux using boot2docker, but in
            # practice that requires extra coordination to make sure
            # $TESTTEMP is going to be visible at the same path to the
            # boot2docker VM. If we figure out how to verify that, we
            # can use the following instead of just saying False:
            # return 'DOCKER_HOST' in os.environ
            return False

        return True
    return False


@check("debhelper", "debian packaging tools")
def has_debhelper():
    # Some versions of dpkg say `dpkg', some say 'dpkg' (` vs ' on the first
    # quote), so just accept anything in that spot.
    dpkg = matchoutput(
        'dpkg --version', br"Debian .dpkg' package management program"
    )
    dh = matchoutput(
        'dh --help', br'dh is a part of debhelper.', ignorestatus=True
    )
    dh_py2 = matchoutput(
        'dh_python2 --help', br'other supported Python versions'
    )
    # debuild comes from the 'devscripts' package, though you might want
    # the 'build-debs' package instead, which has a dependency on devscripts.
    debuild = matchoutput(
        'debuild --help', br'to run debian/rules with given parameter'
    )
    return dpkg and dh and dh_py2 and debuild


@check(
    "debdeps", "debian build dependencies (run dpkg-checkbuilddeps in contrib/)"
)
def has_debdeps():
    # just check exit status (ignoring output)
    path = '%s/../contrib/packaging/debian/control' % os.environ['TESTDIR']
    return matchoutput('dpkg-checkbuilddeps %s' % path, br'')


@check("demandimport", "demandimport enabled")
def has_demandimport():
    # chg disables demandimport intentionally for performance wins.
    return (not has_chg()) and os.environ.get('HGDEMANDIMPORT') != 'disable'


# Add "py27", "py35", ... as possible feature checks. Note that there's no
# punctuation here.
@checkvers("py", "Python >= %s", (2.7, 3.5, 3.6, 3.7, 3.8, 3.9))
def has_python_range(v):
    major, minor = v.split('.')[0:2]
    py_major, py_minor = sys.version_info.major, sys.version_info.minor

    return (py_major, py_minor) >= (int(major), int(minor))


@check("py3", "running with Python 3.x")
def has_py3():
    return 3 == sys.version_info[0]


@check("py3exe", "a Python 3.x interpreter is available")
def has_python3exe():
    return matchoutput('python3 -V', br'^Python 3.(5|6|7|8|9)')


@check("pure", "running with pure Python code")
def has_pure():
    return any(
        [
            os.environ.get("HGMODULEPOLICY") == "py",
            os.environ.get("HGTEST_RUN_TESTS_PURE") == "--pure",
        ]
    )


@check("slow", "allow slow tests (use --allow-slow-tests)")
def has_slow():
    return os.environ.get('HGTEST_SLOW') == 'slow'


@check("hypothesis", "Hypothesis automated test generation")
def has_hypothesis():
    try:
        import hypothesis

        hypothesis.given
        return True
    except ImportError:
        return False


@check("unziplinks", "unzip(1) understands and extracts symlinks")
def unzip_understands_symlinks():
    return matchoutput('unzip --help', br'Info-ZIP')


@check("zstd", "zstd Python module available")
def has_zstd():
    try:
        import mercurial.zstd

        mercurial.zstd.__version__
        return True
    except ImportError:
        return False


@check("devfull", "/dev/full special file")
def has_dev_full():
    return os.path.exists('/dev/full')


@check("ensurepip", "ensurepip module")
def has_ensurepip():
    try:
        import ensurepip

        ensurepip.bootstrap
        return True
    except ImportError:
        return False


@check("virtualenv", "virtualenv support")
def has_virtualenv():
    try:
        import virtualenv

        # --no-site-package became the default in 1.7 (Nov 2011), and the
        # argument was removed in 20.0 (Feb 2020).  Rather than make the
        # script complicated, just ignore ancient versions.
        return int(virtualenv.__version__.split('.')[0]) > 1
    except (AttributeError, ImportError, IndexError):
        return False


@check("fsmonitor", "running tests with fsmonitor")
def has_fsmonitor():
    return 'HGFSMONITOR_TESTS' in os.environ


@check("fuzzywuzzy", "Fuzzy string matching library")
def has_fuzzywuzzy():
    try:
        import fuzzywuzzy

        fuzzywuzzy.__version__
        return True
    except ImportError:
        return False


@check("clang-libfuzzer", "clang new enough to include libfuzzer")
def has_clang_libfuzzer():
    mat = matchoutput('clang --version', br'clang version (\d)')
    if mat:
        # libfuzzer is new in clang 6
        return int(mat.group(1)) > 5
    return False


@check("clang-6.0", "clang 6.0 with version suffix (libfuzzer included)")
def has_clang60():
    return matchoutput('clang-6.0 --version', br'clang version 6\.')


@check("xdiff", "xdiff algorithm")
def has_xdiff():
    try:
        from mercurial import policy

        bdiff = policy.importmod('bdiff')
        return bdiff.xdiffblocks(b'', b'') == [(0, 0, 0, 0)]
    except (ImportError, AttributeError):
        return False


@check('extraextensions', 'whether tests are running with extra extensions')
def has_extraextensions():
    return 'HGTESTEXTRAEXTENSIONS' in os.environ


def getrepofeatures():
    """Obtain set of repository features in use.

    HGREPOFEATURES can be used to define or remove features. It contains
    a space-delimited list of feature strings. Strings beginning with ``-``
    mean to remove.
    """
    # Default list provided by core.
    features = {
        'bundlerepo',
        'revlogstore',
        'fncache',
    }

    # Features that imply other features.
    implies = {
        'simplestore': ['-revlogstore', '-bundlerepo', '-fncache'],
    }

    for override in os.environ.get('HGREPOFEATURES', '').split(' '):
        if not override:
            continue

        if override.startswith('-'):
            if override[1:] in features:
                features.remove(override[1:])
        else:
            features.add(override)

            for imply in implies.get(override, []):
                if imply.startswith('-'):
                    if imply[1:] in features:
                        features.remove(imply[1:])
                else:
                    features.add(imply)

    return features


@check('reporevlogstore', 'repository using the default revlog store')
def has_reporevlogstore():
    return 'revlogstore' in getrepofeatures()


@check('reposimplestore', 'repository using simple storage extension')
def has_reposimplestore():
    return 'simplestore' in getrepofeatures()


@check('repobundlerepo', 'whether we can open bundle files as repos')
def has_repobundlerepo():
    return 'bundlerepo' in getrepofeatures()


@check('repofncache', 'repository has an fncache')
def has_repofncache():
    return 'fncache' in getrepofeatures()


@check('sqlite', 'sqlite3 module and matching cli is available')
def has_sqlite():
    try:
        import sqlite3

        version = sqlite3.sqlite_version_info
    except ImportError:
        return False

    if version < (3, 8, 3):
        # WITH clause not supported
        return False

    return matchoutput('sqlite3 -version', br'^3\.\d+')


@check('vcr', 'vcr http mocking library (pytest-vcr)')
def has_vcr():
    try:
        import vcr

        vcr.VCR
        return True
    except (ImportError, AttributeError):
        pass
    return False


@check('emacs', 'GNU Emacs')
def has_emacs():
    # Our emacs lisp uses `with-eval-after-load` which is new in emacs
    # 24.4, so we allow emacs 24.4, 24.5, and 25+ (24.5 was the last
    # 24 release)
    return matchoutput('emacs --version', b'GNU Emacs 2(4.4|4.5|5|6|7|8|9)')


@check('black', 'the black formatter for python (>= 20.8b1)')
def has_black():
    blackcmd = 'black --version'
    version_regex = b'black, version ([0-9a-b.]+)'
    version = matchoutput(blackcmd, version_regex)
    sv = distutils.version.StrictVersion
    return version and sv(_bytes2sys(version.group(1))) >= sv('20.8b1')


@check('pytype', 'the pytype type checker')
def has_pytype():
    pytypecmd = 'pytype --version'
    version = matchoutput(pytypecmd, b'[0-9a-b.]+')
    sv = distutils.version.StrictVersion
    return version and sv(_bytes2sys(version.group(0))) >= sv('2019.10.17')


@check("rustfmt", "rustfmt tool at version nightly-2020-10-04")
def has_rustfmt():
    # We use Nightly's rustfmt due to current unstable config options.
    return matchoutput(
        '`rustup which --toolchain nightly-2020-10-04 rustfmt` --version',
        b'rustfmt',
    )


@check("cargo", "cargo tool")
def has_cargo():
    return matchoutput('`rustup which cargo` --version', b'cargo')


@check("lzma", "python lzma module")
def has_lzma():
    try:
        import _lzma

        _lzma.FORMAT_XZ
        return True
    except ImportError:
        return False