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