Release 3.0.14

[pinch] / pinch.py

diff --git a/pinch.py b/pinch.py
index b5e3b81567894101a9ee0d9cc9de34f253c15dd1..9e80c01436aa2071501be22e3048f70473ef4aad 100644 (file)
--- a/pinch.py
+++ b/pinch.py
@@ -1,3 +1,10 @@
+# pinch: PIN CHannels - a replacement for `nix-channel --update`
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, version 3.
+
+

 import argparse
 import configparser
 import filecmp
 import argparse
 import configparser
 import filecmp


@@ -34,6 +41,8 @@ from typing import (
     Union,
 )
 
     Union,
 )
 

+import git_cache
+

 # Use xdg module when it's less painful to have as a dependency
 
 
 # Use xdg module when it's less painful to have as a dependency
 
 


@@ -62,7 +71,7 @@ class Verification:
 
     @staticmethod
     def _color(s: str, c: int) -> str:
 
     @staticmethod
     def _color(s: str, c: int) -> str:

-        return '\033[%2dm%s\033[00m' % (c, s)
+        return f'\033[{c:2d}m{s}\033[00m'

 
     def result(self, r: bool) -> None:
         message, color = {True: ('OK ', 92), False: ('FAIL', 91)}[r]
 
     def result(self, r: bool) -> None:
         message, color = {True: ('OK ', 92), False: ('FAIL', 91)}[r]


@@ -127,10 +136,18 @@ def copy_to_nix_store(v: Verification, filename: str) -> str:
     return process.stdout.decode().strip()  # type: ignore  # (for old mypy)
 
 
     return process.stdout.decode().strip()  # type: ignore  # (for old mypy)
 
 

+def symlink_archive(v: Verification, path: str) -> str:
+    with tempfile.TemporaryDirectory() as td:
+        archive_filename = os.path.join(td, 'link.tar.gz')
+        os.symlink(path, os.path.join(td, 'link'))
+        with tarfile.open(archive_filename, mode='x:gz') as t:
+            t.add(os.path.join(td, 'link'), arcname='link')
+        return copy_to_nix_store(v, archive_filename)
+
+

 class AliasSearchPath(NamedTuple):
     alias_of: str
 
 class AliasSearchPath(NamedTuple):
     alias_of: str
 

-    # pylint: disable=no-self-use

     def pin(self, _: Verification, __: Optional[Pin]) -> AliasPin:
         return AliasPin()
 
     def pin(self, _: Verification, __: Optional[Pin]) -> AliasPin:
         return AliasPin()
 


@@ -138,17 +155,11 @@ class AliasSearchPath(NamedTuple):
 class SymlinkSearchPath(NamedTuple):
     path: str
 
 class SymlinkSearchPath(NamedTuple):
     path: str
 

-    # pylint: disable=no-self-use

     def pin(self, _: Verification, __: Optional[Pin]) -> SymlinkPin:
         return SymlinkPin()
 
     def fetch(self, v: Verification, _: Pin) -> str:
     def pin(self, _: Verification, __: Optional[Pin]) -> SymlinkPin:
         return SymlinkPin()
 
     def fetch(self, v: Verification, _: Pin) -> str:

-        with tempfile.TemporaryDirectory() as td:
-            archive_filename = os.path.join(td, 'link.tar.gz')
-            os.symlink(self.path, os.path.join(td, 'link'))
-            with tarfile.open(archive_filename, mode='x:gz') as t:
-                t.add(os.path.join(td, 'link'), arcname='link')
-            return copy_to_nix_store(v, archive_filename)
+        return symlink_archive(v, self.path)

 
 
 class GitSearchPath(NamedTuple):
 
 
 class GitSearchPath(NamedTuple):


@@ -156,17 +167,17 @@ class GitSearchPath(NamedTuple):
     git_repo: str
 
     def pin(self, v: Verification, old_pin: Optional[Pin]) -> GitPin:
     git_repo: str
 
     def pin(self, v: Verification, old_pin: Optional[Pin]) -> GitPin:

+        _, new_revision = git_cache.fetch(self.git_repo, self.git_ref)

         if old_pin is not None:
             assert isinstance(old_pin, GitPin)
         if old_pin is not None:
             assert isinstance(old_pin, GitPin)

-        old_revision = old_pin.git_revision if old_pin is not None else None
-
-        new_revision = git_fetch(v, self, None, old_revision)
+            verify_git_ancestry(v, self, old_pin.git_revision, new_revision)

         return GitPin(release_name=git_revision_name(v, self, new_revision),
                       git_revision=new_revision)
 
     def fetch(self, v: Verification, pin: Pin) -> str:
         assert isinstance(pin, GitPin)
         return GitPin(release_name=git_revision_name(v, self, new_revision),
                       git_revision=new_revision)
 
     def fetch(self, v: Verification, pin: Pin) -> str:
         assert isinstance(pin, GitPin)

-        ensure_git_rev_available(v, self, pin, None)
+        git_cache.ensure_rev_available(
+            self.git_repo, self.git_ref, pin.git_revision)

         return git_get_tarball(v, self, pin)
 
 
         return git_get_tarball(v, self, pin)
 
 


@@ -178,12 +189,17 @@ class ChannelSearchPath(NamedTuple):
     def pin(self, v: Verification, old_pin: Optional[Pin]) -> ChannelPin:
         if old_pin is not None:
             assert isinstance(old_pin, ChannelPin)
     def pin(self, v: Verification, old_pin: Optional[Pin]) -> ChannelPin:
         if old_pin is not None:
             assert isinstance(old_pin, ChannelPin)

-        old_revision = old_pin.git_revision if old_pin is not None else None

 
         channel_html, forwarded_url = fetch_channel(v, self)
         table, new_gitpin = parse_channel(v, channel_html)
 
         channel_html, forwarded_url = fetch_channel(v, self)
         table, new_gitpin = parse_channel(v, channel_html)

+        if old_pin is not None and old_pin.git_revision == new_gitpin.git_revision:
+            return old_pin

         fetch_resources(v, new_gitpin, forwarded_url, table)
         fetch_resources(v, new_gitpin, forwarded_url, table)

-        ensure_git_rev_available(v, self, new_gitpin, old_revision)
+        git_cache.ensure_rev_available(
+            self.git_repo, self.git_ref, new_gitpin.git_revision)
+        if old_pin is not None:
+            verify_git_ancestry(
+                v, self, old_pin.git_revision, new_gitpin.git_revision)

         check_channel_contents(v, self, table, new_gitpin)
         return ChannelPin(
             release_name=new_gitpin.release_name,
         check_channel_contents(v, self, table, new_gitpin)
         return ChannelPin(
             release_name=new_gitpin.release_name,


@@ -191,7 +207,6 @@ class ChannelSearchPath(NamedTuple):
             tarball_sha256=table['nixexprs.tar.xz'].digest,
             git_revision=new_gitpin.git_revision)
 
             tarball_sha256=table['nixexprs.tar.xz'].digest,
             git_revision=new_gitpin.git_revision)
 

-    # pylint: disable=no-self-use

     def fetch(self, v: Verification, pin: Pin) -> str:
         assert isinstance(pin, ChannelPin)
 
     def fetch(self, v: Verification, pin: Pin) -> str:
         assert isinstance(pin, ChannelPin)
 


@@ -236,11 +251,11 @@ def compare(a: str, b: str) -> Tuple[List[str], List[str], List[str]]:
 
 def fetch_channel(
         v: Verification, channel: ChannelSearchPath) -> Tuple[str, str]:
 
 def fetch_channel(
         v: Verification, channel: ChannelSearchPath) -> Tuple[str, str]:

-    v.status('Fetching channel')
-    request = urllib.request.urlopen(channel.channel_url, timeout=10)
-    channel_html = request.read().decode()
-    forwarded_url = request.geturl()
-    v.result(request.status == 200)  # type: ignore  # (for old mypy)
+    v.status(f'Fetching channel from {channel.channel_url}')
+    with urllib.request.urlopen(channel.channel_url, timeout=10) as request:
+        channel_html = request.read().decode()
+        forwarded_url = request.geturl()
+        v.result(request.status == 200)

     v.check('Got forwarded', channel.channel_url != forwarded_url)
     return channel_html, forwarded_url
 
     v.check('Got forwarded', channel.channel_url != forwarded_url)
     return channel_html, forwarded_url
 


@@ -251,15 +266,29 @@ def parse_channel(v: Verification, channel_html: str) \
     d = xml.dom.minidom.parseString(channel_html)
     v.ok()
 
     d = xml.dom.minidom.parseString(channel_html)
     v.ok()
 

-    v.status('Extracting release name:')
-    title_name = d.getElementsByTagName(
-        'title')[0].firstChild.nodeValue.split()[2]
-    h1_name = d.getElementsByTagName('h1')[0].firstChild.nodeValue.split()[2]
-    v.status(title_name)
-    v.result(title_name == h1_name)
-
-    v.status('Extracting git commit:')
+    v.status('Finding release name (1)')
+    title = d.getElementsByTagName('title')[0].firstChild
+    v.result(isinstance(title, xml.dom.minidom.CharacterData))
+    assert isinstance(title, xml.dom.minidom.CharacterData)
+    release_name = title.nodeValue.split()[2]
+    v.status('Finding release name (2)')
+    h1 = d.getElementsByTagName('h1')[0].firstChild
+    v.result(isinstance(h1, xml.dom.minidom.CharacterData))
+    assert isinstance(h1, xml.dom.minidom.CharacterData)
+    v.status('Verifying release name:')
+    v.status(release_name)
+    v.result(release_name == h1.nodeValue.split()[2])
+
+    v.status('Finding git commit')

     git_commit_node = d.getElementsByTagName('tt')[0]
     git_commit_node = d.getElementsByTagName('tt')[0]

+    v.result(
+        isinstance(
+            git_commit_node.firstChild,
+            xml.dom.minidom.CharacterData))
+    assert isinstance(
+        git_commit_node.firstChild,
+        xml.dom.minidom.CharacterData)
+    v.status('Extracting git commit:')

     git_revision = git_commit_node.firstChild.nodeValue
     v.status(git_revision)
     v.ok()
     git_revision = git_commit_node.firstChild.nodeValue
     v.status(git_revision)
     v.ok()


@@ -275,7 +304,7 @@ def parse_channel(v: Verification, channel_html: str) \
         digest = Digest16(row.childNodes[2].firstChild.firstChild.nodeValue)
         table[name] = ChannelTableEntry(url=url, digest=digest, size=size)
     v.ok()
         digest = Digest16(row.childNodes[2].firstChild.firstChild.nodeValue)
         table[name] = ChannelTableEntry(url=url, digest=digest, size=size)
     v.ok()

-    return table, GitPin(release_name=title_name, git_revision=git_revision)
+    return table, GitPin(release_name=release_name, git_revision=git_revision)

 
 
 def digest_string(s: bytes) -> Digest16:
 
 
 def digest_string(s: bytes) -> Digest16:


@@ -291,18 +320,39 @@ def digest_file(filename: str) -> Digest16:
     return Digest16(hasher.hexdigest())
 
 
     return Digest16(hasher.hexdigest())
 
 

+@functools.lru_cache
+def _experimental_flag_needed(v: Verification) -> bool:
+    v.status('Checking Nix version')
+    process = subprocess.run(['nix', '--help'], stdout=subprocess.PIPE)
+    v.result(process.returncode == 0)
+    return b'--experimental-features' in process.stdout
+
+
+def _nix_command(v: Verification) -> List[str]:
+    return ['nix', '--experimental-features',
+            'nix-command'] if _experimental_flag_needed(v) else ['nix']
+
+

 def to_Digest16(v: Verification, digest32: Digest32) -> Digest16:
     v.status('Converting digest to base16')
 def to_Digest16(v: Verification, digest32: Digest32) -> Digest16:
     v.status('Converting digest to base16')

-    process = subprocess.run(
-        ['nix', 'to-base16', '--type', 'sha256', digest32], stdout=subprocess.PIPE)
+    process = subprocess.run(_nix_command(v) + [
+        'to-base16',
+        '--type',
+        'sha256',
+        digest32],
+        stdout=subprocess.PIPE)

     v.result(process.returncode == 0)
     return Digest16(process.stdout.decode().strip())
 
 
 def to_Digest32(v: Verification, digest16: Digest16) -> Digest32:
     v.status('Converting digest to base32')
     v.result(process.returncode == 0)
     return Digest16(process.stdout.decode().strip())
 
 
 def to_Digest32(v: Verification, digest16: Digest16) -> Digest32:
     v.status('Converting digest to base32')

-    process = subprocess.run(
-        ['nix', 'to-base32', '--type', 'sha256', digest16], stdout=subprocess.PIPE)
+    process = subprocess.run(_nix_command(v) + [
+        'to-base32',
+        '--type',
+        'sha256',
+        digest16],
+        stdout=subprocess.PIPE)

     v.result(process.returncode == 0)
     return Digest32(process.stdout.decode().strip())
 
     v.result(process.returncode == 0)
     return Digest32(process.stdout.decode().strip())
 


@@ -311,7 +361,7 @@ def fetch_with_nix_prefetch_url(
         v: Verification,
         url: str,
         digest: Digest16) -> str:
         v: Verification,
         url: str,
         digest: Digest16) -> str:

-    v.status('Fetching %s' % url)
+    v.status(f'Fetching {url}')

     process = subprocess.run(
         ['nix-prefetch-url', '--print-path', url, digest], stdout=subprocess.PIPE)
     v.result(process.returncode == 0)
     process = subprocess.run(
         ['nix-prefetch-url', '--print-path', url, digest], stdout=subprocess.PIPE)
     v.result(process.returncode == 0)


@@ -319,7 +369,7 @@ def fetch_with_nix_prefetch_url(
     assert empty == ''
     v.check("Verifying nix-prefetch-url's digest",
             to_Digest16(v, Digest32(prefetch_digest)) == digest)
     assert empty == ''
     v.check("Verifying nix-prefetch-url's digest",
             to_Digest16(v, Digest32(prefetch_digest)) == digest)

-    v.status("Verifying file digest")
+    v.status(f"Verifying digest of {path}")

     file_digest = digest_file(path)
     v.result(file_digest == digest)
     return path  # type: ignore  # (for old mypy)
     file_digest = digest_file(path)
     v.result(file_digest == digest)
     return path  # type: ignore  # (for old mypy)


@@ -336,123 +386,42 @@ def fetch_resources(
         fields.file = fetch_with_nix_prefetch_url(
             v, fields.absolute_url, fields.digest)
     v.status('Verifying git commit on main page matches git commit in table')
         fields.file = fetch_with_nix_prefetch_url(
             v, fields.absolute_url, fields.digest)
     v.status('Verifying git commit on main page matches git commit in table')

-    v.result(open(table['git-revision'].file).read(999) == pin.git_revision)
-
-
-def git_cachedir(git_repo: str) -> str:
-    return os.path.join(
-        xdg.XDG_CACHE_HOME,
-        'pinch/git',
-        digest_string(git_repo.encode()))
+    with open(table['git-revision'].file, encoding='utf-8') as rev_file:
+        v.result(rev_file.read(999) == pin.git_revision)

 
 
 def tarball_cache_file(channel: TarrableSearchPath, pin: GitPin) -> str:
     return os.path.join(
         xdg.XDG_CACHE_HOME,
         'pinch/git-tarball',
 
 
 def tarball_cache_file(channel: TarrableSearchPath, pin: GitPin) -> str:
     return os.path.join(
         xdg.XDG_CACHE_HOME,
         'pinch/git-tarball',

-        '%s-%s-%s' %
-        (digest_string(channel.git_repo.encode()),
-         pin.git_revision,
-         pin.release_name))
+        f'{digest_string(channel.git_repo.encode())}-{pin.git_revision}-{pin.release_name}')

 
 
 def verify_git_ancestry(
         v: Verification,
         channel: TarrableSearchPath,
 
 
 def verify_git_ancestry(
         v: Verification,
         channel: TarrableSearchPath,

-        new_revision: str,
-        old_revision: Optional[str]) -> None:
-    cachedir = git_cachedir(channel.git_repo)
-    v.status('Verifying rev is an ancestor of ref')
+        old_revision: str,
+        new_revision: str) -> None:
+    cachedir = git_cache.git_cachedir(channel.git_repo)
+    v.status(f'Verifying rev is an ancestor of previous rev {old_revision}')

     process = subprocess.run(['git',
                               '-C',
                               cachedir,
                               'merge-base',
                               '--is-ancestor',
     process = subprocess.run(['git',
                               '-C',
                               cachedir,
                               'merge-base',
                               '--is-ancestor',

-                              new_revision,
-                              channel.git_ref])
+                              old_revision,
+                              new_revision])

     v.result(process.returncode == 0)
 
     v.result(process.returncode == 0)
 

-    if old_revision is not None:
-        v.status(
-            'Verifying rev is an ancestor of previous rev %s' %
-            old_revision)
-        process = subprocess.run(['git',
-                                  '-C',
-                                  cachedir,
-                                  'merge-base',
-                                  '--is-ancestor',
-                                  old_revision,
-                                  new_revision])
-        v.result(process.returncode == 0)

 
 

-
-def git_fetch(
-        v: Verification,
-        channel: TarrableSearchPath,
-        desired_revision: Optional[str],
-        old_revision: Optional[str]) -> str:
-    # It would be nice if we could share the nix git cache, but as of the time
-    # of writing it is transitioning from gitv2 (deprecated) to gitv3 (not ready
-    # yet), and trying to straddle them both is too far into nix implementation
-    # details for my comfort.  So we re-implement here half of nix.fetchGit.
-    # :(
-
-    cachedir = git_cachedir(channel.git_repo)
-    if not os.path.exists(cachedir):
-        v.status("Initializing git repo")
-        process = subprocess.run(
-            ['git', 'init', '--bare', cachedir])
-        v.result(process.returncode == 0)
-
-    v.status('Fetching ref "%s" from %s' % (channel.git_ref, channel.git_repo))
-    # We don't use --force here because we want to abort and freak out if forced
-    # updates are happening.
-    process = subprocess.run(['git',
-                              '-C',
-                              cachedir,
-                              'fetch',
-                              channel.git_repo,
-                              '%s:%s' % (channel.git_ref,
-                                         channel.git_ref)])
-    v.result(process.returncode == 0)
-
-    if desired_revision is not None:
-        v.status('Verifying that fetch retrieved this rev')
-        process = subprocess.run(
-            ['git', '-C', cachedir, 'cat-file', '-e', desired_revision])
-        v.result(process.returncode == 0)
-
-    new_revision = open(
-        os.path.join(
-            cachedir,
-            'refs',
-            'heads',
-            channel.git_ref)).read(999).strip()
-
-    verify_git_ancestry(v, channel, new_revision, old_revision)
-
-    return new_revision
-
-
-def ensure_git_rev_available(
-        v: Verification,
-        channel: TarrableSearchPath,
-        pin: GitPin,
-        old_revision: Optional[str]) -> None:
-    cachedir = git_cachedir(channel.git_repo)
-    if os.path.exists(cachedir):
-        v.status('Checking if we already have this rev:')
-        process = subprocess.run(
-            ['git', '-C', cachedir, 'cat-file', '-e', pin.git_revision])
-        if process.returncode == 0:
-            v.status('yes')
-        if process.returncode == 1:
-            v.status('no')
-        v.result(process.returncode == 0 or process.returncode == 1)
-        if process.returncode == 0:
-            verify_git_ancestry(v, channel, pin.git_revision, old_revision)
-            return
-    git_fetch(v, channel, pin.git_revision, old_revision)
+def broken_symlinks_are_identical(root1: str, root2: str, path: str) -> bool:
+    a = os.path.join(root1, path)
+    b = os.path.join(root2, path)
+    return (os.path.islink(a)
+            and os.path.islink(b)
+            and not os.path.exists(a)
+            and not os.path.exists(b)
+            and os.readlink(a) == os.readlink(b))

 
 
 def compare_tarball_and_git(
 
 
 def compare_tarball_and_git(


@@ -461,38 +430,39 @@ def compare_tarball_and_git(
         channel_contents: str,
         git_contents: str) -> None:
     v.status('Comparing channel tarball with git checkout')
         channel_contents: str,
         git_contents: str) -> None:
     v.status('Comparing channel tarball with git checkout')

-    match, mismatch, errors = compare(os.path.join(
-        channel_contents, pin.release_name), git_contents)
+    tarball_contents = os.path.join(channel_contents, pin.release_name)
+    match, mismatch, errors = compare(tarball_contents, git_contents)

     v.ok()
     v.ok()

-    v.check('%d files match' % len(match), len(match) > 0)
-    v.check('%d files differ' % len(mismatch), len(mismatch) == 0)
+    v.check(f'{len(match)} files match', len(match) > 0)
+    v.check(f'{len(mismatch)} files differ', len(mismatch) == 0)

     expected_errors = [
         '.git-revision',
         '.version-suffix',
         'nixpkgs',
         'programs.sqlite',
         'svn-revision']
     expected_errors = [
         '.git-revision',
         '.version-suffix',
         'nixpkgs',
         'programs.sqlite',
         'svn-revision']

-    benign_errors = []
+    benign_expected_errors = []

     for ee in expected_errors:
         if ee in errors:
             errors.remove(ee)
     for ee in expected_errors:
         if ee in errors:
             errors.remove(ee)

-            benign_errors.append(ee)
+            benign_expected_errors.append(ee)
+    errors = [
+        e for e in errors
+        if not broken_symlinks_are_identical(tarball_contents, git_contents, e)
+    ]

     v.check(
     v.check(

-        '%d unexpected incomparable files' %
-        len(errors),
+        f'{len(errors)} unexpected incomparable files: {errors}',

         len(errors) == 0)
     v.check(
         len(errors) == 0)
     v.check(

-        '(%d of %d expected incomparable files)' %
-        (len(benign_errors),
-         len(expected_errors)),
-        len(benign_errors) == len(expected_errors))
+        f'({len(benign_expected_errors)} of {len(expected_errors)} expected incomparable files)',
+        len(benign_expected_errors) == len(expected_errors))

 
 
 def extract_tarball(
         v: Verification,
         table: Dict[str, ChannelTableEntry],
         dest: str) -> None:
 
 
 def extract_tarball(
         v: Verification,
         table: Dict[str, ChannelTableEntry],
         dest: str) -> None:

-    v.status('Extracting tarball %s' % table['nixexprs.tar.xz'].file)
+    v.status(f"Extracting tarball {table['nixexprs.tar.xz'].file}")

     shutil.unpack_archive(table['nixexprs.tar.xz'].file, dest)
     v.ok()
 
     shutil.unpack_archive(table['nixexprs.tar.xz'].file, dest)
     v.ok()
 


@@ -503,19 +473,15 @@ def git_checkout(
         pin: GitPin,
         dest: str) -> None:
     v.status('Checking out corresponding git revision')
         pin: GitPin,
         dest: str) -> None:
     v.status('Checking out corresponding git revision')

-    git = subprocess.Popen(['git',
-                            '-C',
-                            git_cachedir(channel.git_repo),
-                            'archive',
-                            pin.git_revision],
-                           stdout=subprocess.PIPE)
-    tar = subprocess.Popen(
-        ['tar', 'x', '-C', dest, '-f', '-'], stdin=git.stdout)
-    if git.stdout:
-        git.stdout.close()
-    tar.wait()
-    git.wait()
-    v.result(git.returncode == 0 and tar.returncode == 0)
+    with subprocess.Popen(
+            ['git', '-C', git_cache.git_cachedir(channel.git_repo), 'archive', pin.git_revision],
+            stdout=subprocess.PIPE) as git:
+        with subprocess.Popen(['tar', 'x', '-C', dest, '-f', '-'], stdin=git.stdout) as tar:
+            if git.stdout:
+                git.stdout.close()
+            tar.wait()
+            git.wait()
+            v.result(git.returncode == 0 and tar.returncode == 0)

 
 
 def git_get_tarball(
 
 
 def git_get_tarball(


@@ -524,33 +490,30 @@ def git_get_tarball(
         pin: GitPin) -> str:
     cache_file = tarball_cache_file(channel, pin)
     if os.path.exists(cache_file):
         pin: GitPin) -> str:
     cache_file = tarball_cache_file(channel, pin)
     if os.path.exists(cache_file):

-        cached_tarball = open(cache_file).read(9999)
-        if os.path.exists(cached_tarball):
-            return cached_tarball
+        with open(cache_file, encoding='utf-8') as f:
+            cached_tarball = f.read(9999)
+            if os.path.exists(cached_tarball):
+                return cached_tarball

 
     with tempfile.TemporaryDirectory() as output_dir:
         output_filename = os.path.join(
             output_dir, pin.release_name + '.tar.xz')
 
     with tempfile.TemporaryDirectory() as output_dir:
         output_filename = os.path.join(
             output_dir, pin.release_name + '.tar.xz')

-        with open(output_filename, 'w') as output_file:
-            v.status(
-                'Generating tarball for git revision %s' %
-                pin.git_revision)
-            git = subprocess.Popen(['git',
-                                    '-C',
-                                    git_cachedir(channel.git_repo),
-                                    'archive',
-                                    '--prefix=%s/' % pin.release_name,
-                                    pin.git_revision],
-                                   stdout=subprocess.PIPE)
-            xz = subprocess.Popen(['xz'], stdin=git.stdout, stdout=output_file)
-            xz.wait()
-            git.wait()
-            v.result(git.returncode == 0 and xz.returncode == 0)
+        with open(output_filename, 'w', encoding='utf-8') as output_file:
+            v.status(f'Generating tarball for git revision {pin.git_revision}')
+            with subprocess.Popen(
+                    ['git', '-C', git_cache.git_cachedir(channel.git_repo),
+                        'archive', f'--prefix={pin.release_name}/', pin.git_revision],
+                    stdout=subprocess.PIPE) as git:
+                with subprocess.Popen(['xz'], stdin=git.stdout, stdout=output_file) as xz:
+                    xz.wait()
+                    git.wait()
+                    v.result(git.returncode == 0 and xz.returncode == 0)

 
         store_tarball = copy_to_nix_store(v, output_filename)
 
         os.makedirs(os.path.dirname(cache_file), exist_ok=True)
 
         store_tarball = copy_to_nix_store(v, output_filename)
 
         os.makedirs(os.path.dirname(cache_file), exist_ok=True)

-        open(cache_file, 'w').write(store_tarball)
+        with open(cache_file, 'w', encoding='utf-8') as f:
+            f.write(store_tarball)

         return store_tarball  # type: ignore  # (for old mypy)
 
 
         return store_tarball  # type: ignore  # (for old mypy)
 
 


@@ -559,21 +522,15 @@ def check_channel_metadata(
         pin: GitPin,
         channel_contents: str) -> None:
     v.status('Verifying git commit in channel tarball')
         pin: GitPin,
         channel_contents: str) -> None:
     v.status('Verifying git commit in channel tarball')

-    v.result(
-        open(
-            os.path.join(
-                channel_contents,
-                pin.release_name,
-                '.git-revision')).read(999) == pin.git_revision)
+    with open(os.path.join(channel_contents, pin.release_name, '.git-revision'),
+              encoding='utf-8') as f:
+        v.result(f.read(999) == pin.git_revision)

 
     v.status(
 
     v.status(

-        'Verifying version-suffix is a suffix of release name %s:' %
-        pin.release_name)
-    version_suffix = open(
-        os.path.join(
-            channel_contents,
-            pin.release_name,
-            '.version-suffix')).read(999)
+        f'Verifying version-suffix is a suffix of release name {pin.release_name}:')
+    with open(os.path.join(channel_contents, pin.release_name, '.version-suffix'),
+              encoding='utf-8') as f:
+        version_suffix = f.read(999)

     v.status(version_suffix)
     v.result(pin.release_name.endswith(version_suffix))
 
     v.status(version_suffix)
     v.result(pin.release_name.endswith(version_suffix))
 


@@ -604,7 +561,7 @@ def git_revision_name(
     v.status('Getting commit date')
     process = subprocess.run(['git',
                               '-C',
     v.status('Getting commit date')
     process = subprocess.run(['git',
                               '-C',

-                              git_cachedir(channel.git_repo),
+                              git_cache.git_cachedir(channel.git_repo),

                               'log',
                               '-n1',
                               '--format=%ct-%h',
                               'log',
                               '-n1',
                               '--format=%ct-%h',


@@ -613,8 +570,7 @@ def git_revision_name(
                               git_revision],
                              stdout=subprocess.PIPE)
     v.result(process.returncode == 0 and process.stdout != b'')
                               git_revision],
                              stdout=subprocess.PIPE)
     v.result(process.returncode == 0 and process.stdout != b'')

-    return '%s-%s' % (os.path.basename(channel.git_repo),
-                      process.stdout.decode().strip())
+    return f'{os.path.basename(channel.git_repo)}-{process.stdout.decode().strip()}'

 
 
 K = TypeVar('K')
 
 
 K = TypeVar('K')


@@ -650,7 +606,7 @@ def read_config_section(
     _, all_fields = filter_dict(dict(conf.items()), set(['type']))
     pin_fields, remaining_fields = filter_dict(all_fields, set(P._fields))
     # Error suppression works around https://github.com/python/mypy/issues/9007
     _, all_fields = filter_dict(dict(conf.items()), set(['type']))
     pin_fields, remaining_fields = filter_dict(all_fields, set(P._fields))
     # Error suppression works around https://github.com/python/mypy/issues/9007

-    pin_present = pin_fields != {} or P._fields == ()
+    pin_present = pin_fields or P._fields == ()

     pin = P(**pin_fields) if pin_present else None  # type: ignore
     return SP(**remaining_fields), pin
 
     pin = P(**pin_fields) if pin_present else None  # type: ignore
     return SP(**remaining_fields), pin
 


@@ -659,15 +615,15 @@ def read_pinned_config_section(
         section: str, conf: configparser.SectionProxy) -> Tuple[SearchPath, Pin]:
     sp, pin = read_config_section(conf)
     if pin is None:
         section: str, conf: configparser.SectionProxy) -> Tuple[SearchPath, Pin]:
     sp, pin = read_config_section(conf)
     if pin is None:

-        raise Exception(
-            'Cannot update unpinned channel "%s" (Run "pin" before "update")' %
-            section)
+        raise RuntimeError(
+            f'Cannot update unpinned channel "{section}" (Run "pin" before "update")')

     return sp, pin
 
 
 def read_config(filename: str) -> configparser.ConfigParser:
     config = configparser.ConfigParser()
     return sp, pin
 
 
 def read_config(filename: str) -> configparser.ConfigParser:
     config = configparser.ConfigParser()

-    config.read_file(open(filename), filename)
+    with open(filename, encoding='utf-8') as f:
+        config.read_file(f, filename)

     return config
 
 
     return config
 
 


@@ -678,7 +634,7 @@ def read_config_files(
         config = read_config(file)
         for section in config.sections():
             if section in merged_config:
         config = read_config(file)
         for section in config.sections():
             if section in merged_config:

-                raise Exception('Duplicate channel "%s"' % section)
+                raise RuntimeError('Duplicate channel "{section}"')

             merged_config[section] = config[section]
     return merged_config
 
             merged_config[section] = config[section]
     return merged_config
 


@@ -694,13 +650,18 @@ def pinCommand(args: argparse.Namespace) -> None:
 
         config[section].update(sp.pin(v, old_pin)._asdict())
 
 
         config[section].update(sp.pin(v, old_pin)._asdict())
 

-    with open(args.channels_file, 'w') as configfile:
+    with open(args.channels_file, 'w', encoding='utf-8') as configfile:

         config.write(configfile)
 
 
 def updateCommand(args: argparse.Namespace) -> None:
     v = Verification()
     exprs: Dict[str, str] = {}
         config.write(configfile)
 
 
 def updateCommand(args: argparse.Namespace) -> None:
     v = Verification()
     exprs: Dict[str, str] = {}

+    profile_manifest = os.path.join(args.profile, "manifest.nix")
+    search_paths: List[str] = [
+        "-I", "pinch_profile=" + args.profile,
+        "-I", "pinch_profile_manifest=" + os.readlink(profile_manifest)
+    ] if os.path.exists(profile_manifest) else []

     config = {
         section: read_pinned_config_section(section, conf) for section,
         conf in read_config_files(
     config = {
         section: read_pinned_config_section(section, conf) for section,
         conf in read_config_files(


@@ -708,13 +669,15 @@ def updateCommand(args: argparse.Namespace) -> None:
     alias, nonalias = partition_dict(
         lambda k, v: isinstance(v[0], AliasSearchPath), config)
 
     alias, nonalias = partition_dict(
         lambda k, v: isinstance(v[0], AliasSearchPath), config)
 

-    for section, (sp, pin) in nonalias.items():
+    for section, (sp, pin) in sorted(nonalias.items()):

         assert not isinstance(sp, AliasSearchPath)  # mypy can't see through
         assert not isinstance(pin, AliasPin)        # partition_dict()
         tarball = sp.fetch(v, pin)
         assert not isinstance(sp, AliasSearchPath)  # mypy can't see through
         assert not isinstance(pin, AliasPin)        # partition_dict()
         tarball = sp.fetch(v, pin)

+        search_paths.extend(
+            ["-I", f"pinch_tarball_for_{pin.release_name}={tarball}"])

         exprs[section] = (
         exprs[section] = (

-            'f: f { name = "%s"; channelName = "%%s"; src = builtins.storePath "%s"; }' %
-            (pin.release_name, tarball))
+            f'f: f {{ name = "{pin.release_name}"; channelName = "%s"; '
+            f'src = builtins.storePath "{tarball}"; }}')

 
     for section, (sp, pin) in alias.items():
         assert isinstance(sp, AliasSearchPath)  # For mypy
 
     for section, (sp, pin) in alias.items():
         assert isinstance(sp, AliasSearchPath)  # For mypy


@@ -723,13 +686,14 @@ def updateCommand(args: argparse.Namespace) -> None:
     command = [
         'nix-env',
         '--profile',
     command = [
         'nix-env',
         '--profile',

-        '/nix/var/nix/profiles/per-user/%s/channels' %
-        getpass.getuser(),
+        args.profile,

         '--show-trace',
         '--file',
         '<nix/unpack-channel.nix>',
         '--install',
         '--show-trace',
         '--file',
         '<nix/unpack-channel.nix>',
         '--install',

-        '--from-expression'] + [exprs[name] % name for name in sorted(exprs.keys())]
+        '--remove-all',
+    ] + search_paths + ['--from-expression'] + [
+        exprs[name] % name for name in sorted(exprs.keys())]

     if args.dry_run:
         print(' '.join(map(shlex.quote, command)))
     else:
     if args.dry_run:
         print(' '.join(map(shlex.quote, command)))
     else:


@@ -747,6 +711,8 @@ def main() -> None:
     parser_pin.set_defaults(func=pinCommand)
     parser_update = subparsers.add_parser('update')
     parser_update.add_argument('--dry-run', action='store_true')
     parser_pin.set_defaults(func=pinCommand)
     parser_update = subparsers.add_parser('update')
     parser_update.add_argument('--dry-run', action='store_true')

+    parser_update.add_argument('--profile', default=(
+        f'/nix/var/nix/profiles/per-user/{getpass.getuser()}/channels'))

     parser_update.add_argument('channels_file', type=str, nargs='+')
     parser_update.set_defaults(func=updateCommand)
     args = parser.parse_args()
     parser_update.add_argument('channels_file', type=str, nargs='+')
     parser_update.set_defaults(func=updateCommand)
     args = parser.parse_args()