Add --dry_run flag

diff --git a/pinch.py b/pinch.py
index 8bda816bd2c2d80f86bb7ae8416cefe95d4aa998..4a6158adb7a7907537d10a9f5273ccc6bd2fafc3 100644 (file)
--- a/pinch.py
+++ b/pinch.py
@@ -7,6 +7,7 @@ import hashlib
 import operator
 import os
 import os.path
+import shlex
 import shutil
 import subprocess
 import tempfile
@@ -497,20 +498,22 @@ def update(args: argparse.Namespace) -> None:
         exprs.append(
             'f: f { name = "%s"; channelName = "%s"; src = builtins.storePath "%s"; }' %
             (config[section]['release_name'], section, tarball))
-    v.status('Installing channels with nix-env')
-    process = subprocess.run(
-        [
-            'nix-env',
-            '--profile',
-            '/nix/var/nix/profiles/per-user/%s/channels' %
-            getpass.getuser(),
-            '--show-trace',
-            '--file',
-            '<nix/unpack-channel.nix>',
-            '--install',
-            '--from-expression'] +
-        exprs)
-    v.result(process.returncode == 0)
+    command = [
+        'nix-env',
+        '--profile',
+        '/nix/var/nix/profiles/per-user/%s/channels' %
+        getpass.getuser(),
+        '--show-trace',
+        '--file',
+        '<nix/unpack-channel.nix>',
+        '--install',
+        '--from-expression'] + exprs
+    if args.dry_run:
+        print(' '.join(map(shlex.quote, command)))
+    else:
+        v.status('Installing channels with nix-env')
+        process = subprocess.run(command)
+        v.result(process.returncode == 0)
 
 
 def main() -> None:
@@ -521,6 +524,7 @@ def main() -> None:
     parser_pin.add_argument('channels', type=str, nargs='*')
     parser_pin.set_defaults(func=pin)
     parser_update = subparsers.add_parser('update')
+    parser_update.add_argument('--dry-run', action='store_true')
     parser_update.add_argument('channels_file', type=str)
     parser_update.set_defaults(func=update)
     args = parser.parse_args()