git.scottworley.com Git - pinch/blob - pinch.py

   1 import argparse
   2 import configparser
   3 import filecmp
   4 import functools
   5 import getpass
   6 import hashlib
   7 import operator
   8 import os
   9 import os.path
  10 import shlex
  11 import shutil
  12 import subprocess
  13 import sys
  14 import tempfile
  15 import types
  16 import urllib.parse
  17 import urllib.request
  18 import xml.dom.minidom
  19
  20 from typing import (
  21     Dict,
  22     Iterable,
  23     List,
  24     Mapping,
  25     NamedTuple,
  26     NewType,
  27     Optional,
  28     Set,
  29     Tuple,
  30     Type,
  31     TypeVar,
  32     Union,
  33 )
  34
  35 # Use xdg module when it's less painful to have as a dependency
  36
  37
  38 class XDG(NamedTuple):
  39     XDG_CACHE_HOME: str
  40
  41
  42 xdg = XDG(
  43     XDG_CACHE_HOME=os.getenv(
  44         'XDG_CACHE_HOME',
  45         os.path.expanduser('~/.cache')))
  46
  47
  48 class VerificationError(Exception):
  49     pass
  50
  51
  52 class Verification:
  53
  54     def __init__(self) -> None:
  55         self.line_length = 0
  56
  57     def status(self, s: str) -> None:
  58         print(s, end=' ', file=sys.stderr, flush=True)
  59         self.line_length += 1 + len(s)  # Unicode??
  60
  61     @staticmethod
  62     def _color(s: str, c: int) -> str:
  63         return '\033[%2dm%s\033[00m' % (c, s)
  64
  65     def result(self, r: bool) -> None:
  66         message, color = {True: ('OK ', 92), False: ('FAIL', 91)}[r]
  67         length = len(message)
  68         cols = shutil.get_terminal_size().columns or 80
  69         pad = (cols - (self.line_length + length)) % cols
  70         print(' ' * pad + self._color(message, color), file=sys.stderr)
  71         self.line_length = 0
  72         if not r:
  73             raise VerificationError()
  74
  75     def check(self, s: str, r: bool) -> None:
  76         self.status(s)
  77         self.result(r)
  78
  79     def ok(self) -> None:
  80         self.result(True)
  81
  82
  83 Digest16 = NewType('Digest16', str)
  84 Digest32 = NewType('Digest32', str)
  85
  86
  87 class ChannelTableEntry(types.SimpleNamespace):
  88     absolute_url: str
  89     digest: Digest16
  90     file: str
  91     size: int
  92     url: str
  93
  94
  95 class AliasPin(NamedTuple):
  96     pass
  97
  98
  99 class GitPin(NamedTuple):
 100     git_revision: str
 101     release_name: str
 102
 103
 104 class ChannelPin(NamedTuple):
 105     git_revision: str
 106     release_name: str
 107     tarball_url: str
 108     tarball_sha256: str
 109
 110
 111 Pin = Union[AliasPin, GitPin, ChannelPin]
 112
 113
 114 class AliasSearchPath(NamedTuple):
 115     alias_of: str
 116
 117     # pylint: disable=no-self-use
 118     def pin(self, _: Verification, __: Optional[Pin]) -> AliasPin:
 119         return AliasPin()
 120
 121
 122 class GitSearchPath(NamedTuple):
 123     git_ref: str
 124     git_repo: str
 125
 126     def pin(self, v: Verification, old_pin: Optional[Pin]) -> GitPin:
 127         if old_pin is not None:
 128             assert isinstance(old_pin, GitPin)
 129         old_revision = old_pin.git_revision if old_pin is not None else None
 130
 131         new_revision = git_fetch(v, self, None, old_revision)
 132         return GitPin(release_name=git_revision_name(v, self, new_revision),
 133                       git_revision=new_revision)
 134
 135     def fetch(self, v: Verification, pin: Pin) -> str:
 136         assert isinstance(pin, GitPin)
 137         ensure_git_rev_available(v, self, pin, None)
 138         return git_get_tarball(v, self, pin)
 139
 140
 141 class ChannelSearchPath(NamedTuple):
 142     channel_url: str
 143     git_ref: str
 144     git_repo: str
 145
 146     def pin(self, v: Verification, old_pin: Optional[Pin]) -> ChannelPin:
 147         if old_pin is not None:
 148             assert isinstance(old_pin, ChannelPin)
 149         old_revision = old_pin.git_revision if old_pin is not None else None
 150
 151         channel_html, forwarded_url = fetch_channel(v, self)
 152         table, new_gitpin = parse_channel(v, channel_html)
 153         fetch_resources(v, new_gitpin, forwarded_url, table)
 154         ensure_git_rev_available(v, self, new_gitpin, old_revision)
 155         check_channel_contents(v, self, table, new_gitpin)
 156         return ChannelPin(
 157             release_name=new_gitpin.release_name,
 158             tarball_url=table['nixexprs.tar.xz'].absolute_url,
 159             tarball_sha256=table['nixexprs.tar.xz'].digest,
 160             git_revision=new_gitpin.git_revision)
 161
 162     # pylint: disable=no-self-use
 163     def fetch(self, v: Verification, pin: Pin) -> str:
 164         assert isinstance(pin, ChannelPin)
 165
 166         return fetch_with_nix_prefetch_url(
 167             v, pin.tarball_url, Digest16(pin.tarball_sha256))
 168
 169
 170 SearchPath = Union[AliasSearchPath, GitSearchPath, ChannelSearchPath]
 171 TarrableSearchPath = Union[GitSearchPath, ChannelSearchPath]
 172
 173
 174 def compare(a: str, b: str) -> Tuple[List[str], List[str], List[str]]:
 175
 176     def throw(error: OSError) -> None:
 177         raise error
 178
 179     def join(x: str, y: str) -> str:
 180         return y if x == '.' else os.path.join(x, y)
 181
 182     def recursive_files(d: str) -> Iterable[str]:
 183         all_files: List[str] = []
 184         for path, dirs, files in os.walk(d, onerror=throw):
 185             rel = os.path.relpath(path, start=d)
 186             all_files.extend(join(rel, f) for f in files)
 187             for dir_or_link in dirs:
 188                 if os.path.islink(join(path, dir_or_link)):
 189                     all_files.append(join(rel, dir_or_link))
 190         return all_files
 191
 192     def exclude_dot_git(files: Iterable[str]) -> Iterable[str]:
 193         return (f for f in files if not f.startswith('.git/'))
 194
 195     files = functools.reduce(
 196         operator.or_, (set(
 197             exclude_dot_git(
 198                 recursive_files(x))) for x in [a, b]))
 199     return filecmp.cmpfiles(a, b, files, shallow=False)
 200
 201
 202 def fetch_channel(
 203         v: Verification, channel: ChannelSearchPath) -> Tuple[str, str]:
 204     v.status('Fetching channel')
 205     request = urllib.request.urlopen(channel.channel_url, timeout=10)
 206     channel_html = request.read()
 207     forwarded_url = request.geturl()
 208     v.result(request.status == 200)  # type: ignore  # (for old mypy)
 209     v.check('Got forwarded', channel.channel_url != forwarded_url)
 210     return channel_html, forwarded_url
 211
 212
 213 def parse_channel(v: Verification, channel_html: str) \
 214         -> Tuple[Dict[str, ChannelTableEntry], GitPin]:
 215     v.status('Parsing channel description as XML')
 216     d = xml.dom.minidom.parseString(channel_html)
 217     v.ok()
 218
 219     v.status('Extracting release name:')
 220     title_name = d.getElementsByTagName(
 221         'title')[0].firstChild.nodeValue.split()[2]
 222     h1_name = d.getElementsByTagName('h1')[0].firstChild.nodeValue.split()[2]
 223     v.status(title_name)
 224     v.result(title_name == h1_name)
 225
 226     v.status('Extracting git commit:')
 227     git_commit_node = d.getElementsByTagName('tt')[0]
 228     git_revision = git_commit_node.firstChild.nodeValue
 229     v.status(git_revision)
 230     v.ok()
 231     v.status('Verifying git commit label')
 232     v.result(git_commit_node.previousSibling.nodeValue == 'Git commit ')
 233
 234     v.status('Parsing table')
 235     table: Dict[str, ChannelTableEntry] = {}
 236     for row in d.getElementsByTagName('tr')[1:]:
 237         name = row.childNodes[0].firstChild.firstChild.nodeValue
 238         url = row.childNodes[0].firstChild.getAttribute('href')
 239         size = int(row.childNodes[1].firstChild.nodeValue)
 240         digest = Digest16(row.childNodes[2].firstChild.firstChild.nodeValue)
 241         table[name] = ChannelTableEntry(url=url, digest=digest, size=size)
 242     v.ok()
 243     return table, GitPin(release_name=title_name, git_revision=git_revision)
 244
 245
 246 def digest_string(s: bytes) -> Digest16:
 247     return Digest16(hashlib.sha256(s).hexdigest())
 248
 249
 250 def digest_file(filename: str) -> Digest16:
 251     hasher = hashlib.sha256()
 252     with open(filename, 'rb') as f:
 253         # pylint: disable=cell-var-from-loop
 254         for block in iter(lambda: f.read(4096), b''):
 255             hasher.update(block)
 256     return Digest16(hasher.hexdigest())
 257
 258
 259 def to_Digest16(v: Verification, digest32: Digest32) -> Digest16:
 260     v.status('Converting digest to base16')
 261     process = subprocess.run(
 262         ['nix', 'to-base16', '--type', 'sha256', digest32], stdout=subprocess.PIPE)
 263     v.result(process.returncode == 0)
 264     return Digest16(process.stdout.decode().strip())
 265
 266
 267 def to_Digest32(v: Verification, digest16: Digest16) -> Digest32:
 268     v.status('Converting digest to base32')
 269     process = subprocess.run(
 270         ['nix', 'to-base32', '--type', 'sha256', digest16], stdout=subprocess.PIPE)
 271     v.result(process.returncode == 0)
 272     return Digest32(process.stdout.decode().strip())
 273
 274
 275 def fetch_with_nix_prefetch_url(
 276         v: Verification,
 277         url: str,
 278         digest: Digest16) -> str:
 279     v.status('Fetching %s' % url)
 280     process = subprocess.run(
 281         ['nix-prefetch-url', '--print-path', url, digest], stdout=subprocess.PIPE)
 282     v.result(process.returncode == 0)
 283     prefetch_digest, path, empty = process.stdout.decode().split('\n')
 284     assert empty == ''
 285     v.check("Verifying nix-prefetch-url's digest",
 286             to_Digest16(v, Digest32(prefetch_digest)) == digest)
 287     v.status("Verifying file digest")
 288     file_digest = digest_file(path)
 289     v.result(file_digest == digest)
 290     return path  # type: ignore  # (for old mypy)
 291
 292
 293 def fetch_resources(
 294         v: Verification,
 295         pin: GitPin,
 296         forwarded_url: str,
 297         table: Dict[str, ChannelTableEntry]) -> None:
 298     for resource in ['git-revision', 'nixexprs.tar.xz']:
 299         fields = table[resource]
 300         fields.absolute_url = urllib.parse.urljoin(forwarded_url, fields.url)
 301         fields.file = fetch_with_nix_prefetch_url(
 302             v, fields.absolute_url, fields.digest)
 303     v.status('Verifying git commit on main page matches git commit in table')
 304     v.result(open(table['git-revision'].file).read(999) == pin.git_revision)
 305
 306
 307 def git_cachedir(git_repo: str) -> str:
 308     return os.path.join(
 309         xdg.XDG_CACHE_HOME,
 310         'pinch/git',
 311         digest_string(git_repo.encode()))
 312
 313
 314 def tarball_cache_file(channel: TarrableSearchPath, pin: GitPin) -> str:
 315     return os.path.join(
 316         xdg.XDG_CACHE_HOME,
 317         'pinch/git-tarball',
 318         '%s-%s-%s' %
 319         (digest_string(channel.git_repo.encode()),
 320          pin.git_revision,
 321          pin.release_name))
 322
 323
 324 def verify_git_ancestry(
 325         v: Verification,
 326         channel: TarrableSearchPath,
 327         new_revision: str,
 328         old_revision: Optional[str]) -> None:
 329     cachedir = git_cachedir(channel.git_repo)
 330     v.status('Verifying rev is an ancestor of ref')
 331     process = subprocess.run(['git',
 332                               '-C',
 333                               cachedir,
 334                               'merge-base',
 335                               '--is-ancestor',
 336                               new_revision,
 337                               channel.git_ref])
 338     v.result(process.returncode == 0)
 339
 340     if old_revision is not None:
 341         v.status(
 342             'Verifying rev is an ancestor of previous rev %s' %
 343             old_revision)
 344         process = subprocess.run(['git',
 345                                   '-C',
 346                                   cachedir,
 347                                   'merge-base',
 348                                   '--is-ancestor',
 349                                   old_revision,
 350                                   new_revision])
 351         v.result(process.returncode == 0)
 352
 353
 354 def git_fetch(
 355         v: Verification,
 356         channel: TarrableSearchPath,
 357         desired_revision: Optional[str],
 358         old_revision: Optional[str]) -> str:
 359     # It would be nice if we could share the nix git cache, but as of the time
 360     # of writing it is transitioning from gitv2 (deprecated) to gitv3 (not ready
 361     # yet), and trying to straddle them both is too far into nix implementation
 362     # details for my comfort.  So we re-implement here half of nix.fetchGit.
 363     # :(
 364
 365     cachedir = git_cachedir(channel.git_repo)
 366     if not os.path.exists(cachedir):
 367         v.status("Initializing git repo")
 368         process = subprocess.run(
 369             ['git', 'init', '--bare', cachedir])
 370         v.result(process.returncode == 0)
 371
 372     v.status('Fetching ref "%s" from %s' % (channel.git_ref, channel.git_repo))
 373     # We don't use --force here because we want to abort and freak out if forced
 374     # updates are happening.
 375     process = subprocess.run(['git',
 376                               '-C',
 377                               cachedir,
 378                               'fetch',
 379                               channel.git_repo,
 380                               '%s:%s' % (channel.git_ref,
 381                                          channel.git_ref)])
 382     v.result(process.returncode == 0)
 383
 384     if desired_revision is not None:
 385         v.status('Verifying that fetch retrieved this rev')
 386         process = subprocess.run(
 387             ['git', '-C', cachedir, 'cat-file', '-e', desired_revision])
 388         v.result(process.returncode == 0)
 389
 390     new_revision = open(
 391         os.path.join(
 392             cachedir,
 393             'refs',
 394             'heads',
 395             channel.git_ref)).read(999).strip()
 396
 397     verify_git_ancestry(v, channel, new_revision, old_revision)
 398
 399     return new_revision
 400
 401
 402 def ensure_git_rev_available(
 403         v: Verification,
 404         channel: TarrableSearchPath,
 405         pin: GitPin,
 406         old_revision: Optional[str]) -> None:
 407     cachedir = git_cachedir(channel.git_repo)
 408     if os.path.exists(cachedir):
 409         v.status('Checking if we already have this rev:')
 410         process = subprocess.run(
 411             ['git', '-C', cachedir, 'cat-file', '-e', pin.git_revision])
 412         if process.returncode == 0:
 413             v.status('yes')
 414         if process.returncode == 1:
 415             v.status('no')
 416         v.result(process.returncode == 0 or process.returncode == 1)
 417         if process.returncode == 0:
 418             verify_git_ancestry(v, channel, pin.git_revision, old_revision)
 419             return
 420     git_fetch(v, channel, pin.git_revision, old_revision)
 421
 422
 423 def compare_tarball_and_git(
 424         v: Verification,
 425         pin: GitPin,
 426         channel_contents: str,
 427         git_contents: str) -> None:
 428     v.status('Comparing channel tarball with git checkout')
 429     match, mismatch, errors = compare(os.path.join(
 430         channel_contents, pin.release_name), git_contents)
 431     v.ok()
 432     v.check('%d files match' % len(match), len(match) > 0)
 433     v.check('%d files differ' % len(mismatch), len(mismatch) == 0)
 434     expected_errors = [
 435         '.git-revision',
 436         '.version-suffix',
 437         'nixpkgs',
 438         'programs.sqlite',
 439         'svn-revision']
 440     benign_errors = []
 441     for ee in expected_errors:
 442         if ee in errors:
 443             errors.remove(ee)
 444             benign_errors.append(ee)
 445     v.check(
 446         '%d unexpected incomparable files' %
 447         len(errors),
 448         len(errors) == 0)
 449     v.check(
 450         '(%d of %d expected incomparable files)' %
 451         (len(benign_errors),
 452          len(expected_errors)),
 453         len(benign_errors) == len(expected_errors))
 454
 455
 456 def extract_tarball(
 457         v: Verification,
 458         table: Dict[str, ChannelTableEntry],
 459         dest: str) -> None:
 460     v.status('Extracting tarball %s' % table['nixexprs.tar.xz'].file)
 461     shutil.unpack_archive(table['nixexprs.tar.xz'].file, dest)
 462     v.ok()
 463
 464
 465 def git_checkout(
 466         v: Verification,
 467         channel: TarrableSearchPath,
 468         pin: GitPin,
 469         dest: str) -> None:
 470     v.status('Checking out corresponding git revision')
 471     git = subprocess.Popen(['git',
 472                             '-C',
 473                             git_cachedir(channel.git_repo),
 474                             'archive',
 475                             pin.git_revision],
 476                            stdout=subprocess.PIPE)
 477     tar = subprocess.Popen(
 478         ['tar', 'x', '-C', dest, '-f', '-'], stdin=git.stdout)
 479     if git.stdout:
 480         git.stdout.close()
 481     tar.wait()
 482     git.wait()
 483     v.result(git.returncode == 0 and tar.returncode == 0)
 484
 485
 486 def git_get_tarball(
 487         v: Verification,
 488         channel: TarrableSearchPath,
 489         pin: GitPin) -> str:
 490     cache_file = tarball_cache_file(channel, pin)
 491     if os.path.exists(cache_file):
 492         cached_tarball = open(cache_file).read(9999)
 493         if os.path.exists(cached_tarball):
 494             return cached_tarball
 495
 496     with tempfile.TemporaryDirectory() as output_dir:
 497         output_filename = os.path.join(
 498             output_dir, pin.release_name + '.tar.xz')
 499         with open(output_filename, 'w') as output_file:
 500             v.status(
 501                 'Generating tarball for git revision %s' %
 502                 pin.git_revision)
 503             git = subprocess.Popen(['git',
 504                                     '-C',
 505                                     git_cachedir(channel.git_repo),
 506                                     'archive',
 507                                     '--prefix=%s/' % pin.release_name,
 508                                     pin.git_revision],
 509                                    stdout=subprocess.PIPE)
 510             xz = subprocess.Popen(['xz'], stdin=git.stdout, stdout=output_file)
 511             xz.wait()
 512             git.wait()
 513             v.result(git.returncode == 0 and xz.returncode == 0)
 514
 515         v.status('Putting tarball in Nix store')
 516         process = subprocess.run(
 517             ['nix-store', '--add', output_filename], stdout=subprocess.PIPE)
 518         v.result(process.returncode == 0)
 519         store_tarball = process.stdout.decode().strip()
 520
 521         os.makedirs(os.path.dirname(cache_file), exist_ok=True)
 522         open(cache_file, 'w').write(store_tarball)
 523         return store_tarball  # type: ignore  # (for old mypy)
 524
 525
 526 def check_channel_metadata(
 527         v: Verification,
 528         pin: GitPin,
 529         channel_contents: str) -> None:
 530     v.status('Verifying git commit in channel tarball')
 531     v.result(
 532         open(
 533             os.path.join(
 534                 channel_contents,
 535                 pin.release_name,
 536                 '.git-revision')).read(999) == pin.git_revision)
 537
 538     v.status(
 539         'Verifying version-suffix is a suffix of release name %s:' %
 540         pin.release_name)
 541     version_suffix = open(
 542         os.path.join(
 543             channel_contents,
 544             pin.release_name,
 545             '.version-suffix')).read(999)
 546     v.status(version_suffix)
 547     v.result(pin.release_name.endswith(version_suffix))
 548
 549
 550 def check_channel_contents(
 551         v: Verification,
 552         channel: TarrableSearchPath,
 553         table: Dict[str, ChannelTableEntry],
 554         pin: GitPin) -> None:
 555     with tempfile.TemporaryDirectory() as channel_contents, \
 556             tempfile.TemporaryDirectory() as git_contents:
 557
 558         extract_tarball(v, table, channel_contents)
 559         check_channel_metadata(v, pin, channel_contents)
 560
 561         git_checkout(v, channel, pin, git_contents)
 562
 563         compare_tarball_and_git(v, pin, channel_contents, git_contents)
 564
 565         v.status('Removing temporary directories')
 566     v.ok()
 567
 568
 569 def git_revision_name(
 570         v: Verification,
 571         channel: TarrableSearchPath,
 572         git_revision: str) -> str:
 573     v.status('Getting commit date')
 574     process = subprocess.run(['git',
 575                               '-C',
 576                               git_cachedir(channel.git_repo),
 577                               'log',
 578                               '-n1',
 579                               '--format=%ct-%h',
 580                               '--abbrev=11',
 581                               '--no-show-signature',
 582                               git_revision],
 583                              stdout=subprocess.PIPE)
 584     v.result(process.returncode == 0 and process.stdout != b'')
 585     return '%s-%s' % (os.path.basename(channel.git_repo),
 586                       process.stdout.decode().strip())
 587
 588
 589 K = TypeVar('K')
 590 V = TypeVar('V')
 591
 592
 593 def filter_dict(d: Dict[K, V], fields: Set[K]
 594                 ) -> Tuple[Dict[K, V], Dict[K, V]]:
 595     selected: Dict[K, V] = {}
 596     remaining: Dict[K, V] = {}
 597     for k, v in d.items():
 598         if k in fields:
 599             selected[k] = v
 600         else:
 601             remaining[k] = v
 602     return selected, remaining
 603
 604
 605 def read_config_section(
 606         conf: configparser.SectionProxy) -> Tuple[SearchPath, Optional[Pin]]:
 607     mapping: Mapping[str, Tuple[Type[SearchPath], Type[Pin]]] = {
 608         'alias': (AliasSearchPath, AliasPin),
 609         'channel': (ChannelSearchPath, ChannelPin),
 610         'git': (GitSearchPath, GitPin),
 611     }
 612     SP, P = mapping[conf['type']]
 613     _, all_fields = filter_dict(dict(conf.items()), set(['type']))
 614     pin_fields, remaining_fields = filter_dict(all_fields, set(P._fields))
 615     # Error suppression works around https://github.com/python/mypy/issues/9007
 616     pin_present = pin_fields != {} or P._fields == ()
 617     pin = P(**pin_fields) if pin_present else None  # type:ignore[call-arg]
 618     return SP(**remaining_fields), pin
 619
 620
 621 def read_pinned_config_section(
 622         section: str, conf: configparser.SectionProxy) -> Tuple[SearchPath, Pin]:
 623     sp, pin = read_config_section(conf)
 624     if pin is None:
 625         raise Exception(
 626             'Cannot update unpinned channel "%s" (Run "pin" before "update")' %
 627             section)
 628     return sp, pin
 629
 630
 631 def read_config(filename: str) -> configparser.ConfigParser:
 632     config = configparser.ConfigParser()
 633     config.read_file(open(filename), filename)
 634     return config
 635
 636
 637 def read_config_files(
 638         filenames: Iterable[str]) -> Dict[str, configparser.SectionProxy]:
 639     merged_config: Dict[str, configparser.SectionProxy] = {}
 640     for file in filenames:
 641         config = read_config(file)
 642         for section in config.sections():
 643             if section in merged_config:
 644                 raise Exception('Duplicate channel "%s"' % section)
 645             merged_config[section] = config[section]
 646     return merged_config
 647
 648
 649 def pinCommand(args: argparse.Namespace) -> None:
 650     v = Verification()
 651     config = read_config(args.channels_file)
 652     for section in config.sections():
 653         if args.channels and section not in args.channels:
 654             continue
 655
 656         sp, old_pin = read_config_section(config[section])
 657
 658         config[section].update(sp.pin(v, old_pin)._asdict())
 659
 660     with open(args.channels_file, 'w') as configfile:
 661         config.write(configfile)
 662
 663
 664 def updateCommand(args: argparse.Namespace) -> None:
 665     v = Verification()
 666     exprs: Dict[str, str] = {}
 667     config = read_config_files(args.channels_file)
 668     for section in config:
 669         sp, pin = read_pinned_config_section(section, config[section])
 670         if isinstance(sp, AliasSearchPath):
 671             continue
 672         tarball = sp.fetch(v, pin)
 673         exprs[section] = (
 674             'f: f { name = "%s"; channelName = "%%s"; src = builtins.storePath "%s"; }' %
 675             (config[section]['release_name'], tarball))
 676
 677     for section in config:
 678         if 'alias_of' in config[section]:
 679             exprs[section] = exprs[str(config[section]['alias_of'])]
 680
 681     command = [
 682         'nix-env',
 683         '--profile',
 684         '/nix/var/nix/profiles/per-user/%s/channels' %
 685         getpass.getuser(),
 686         '--show-trace',
 687         '--file',
 688         '<nix/unpack-channel.nix>',
 689         '--install',
 690         '--from-expression'] + [exprs[name] % name for name in sorted(exprs.keys())]
 691     if args.dry_run:
 692         print(' '.join(map(shlex.quote, command)))
 693     else:
 694         v.status('Installing channels with nix-env')
 695         process = subprocess.run(command)
 696         v.result(process.returncode == 0)
 697
 698
 699 def main() -> None:
 700     parser = argparse.ArgumentParser(prog='pinch')
 701     subparsers = parser.add_subparsers(dest='mode', required=True)
 702     parser_pin = subparsers.add_parser('pin')
 703     parser_pin.add_argument('channels_file', type=str)
 704     parser_pin.add_argument('channels', type=str, nargs='*')
 705     parser_pin.set_defaults(func=pinCommand)
 706     parser_update = subparsers.add_parser('update')
 707     parser_update.add_argument('--dry-run', action='store_true')
 708     parser_update.add_argument('channels_file', type=str, nargs='+')
 709     parser_update.set_defaults(func=updateCommand)
 710     args = parser.parse_args()
 711     args.func(args)
 712
 713
 714 if __name__ == '__main__':
 715     main()