hook: enable calling out of tree entries

in the following setup

├── common
│   ├── .pre-commit-config.yaml
│   ├── script1.sh
│   └── script-config
├── repo1
│   └── code_file
└── repo2
    └── code_file

a common configuration from 'common' folder will be installed using an
absolute path to repo1 and repo2.
As local tools needs to be run (script1.sh with its
configuration script-config) we need to pass the path to common
somehow into the hook cmdline.

Add support for a template variable %CONFIG_BASEPATH% which
is automatically expanded to the configuration directory when
pre-commit run is called

This helps to create a single source of truth setup, while still
keeping the possibility to call non public tools and configurations

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>

pre_commit/commands/run.py

@@ -397,7 +397,7 @@ def run(
 
         config = load_config(config_file)
         hooks = [
-            hook
+            hook.expand(args, config_file)
             for hook in all_hooks(config, store)
             if not args.hook or hook.id == args.hook or hook.alias == args.hook
             if args.hook_stage in hook.stages

pre_commit/hook.py

@@ -1,6 +1,8 @@
 from __future__ import annotations
 
+import argparse
 import logging
+import os
 import shlex
 from typing import Any
 from typing import NamedTuple
@@ -61,5 +63,15 @@ class Hook(NamedTuple):
             )
         return cls(src=src, prefix=prefix, **{k: dct[k] for k in _KEYS})
 
+    def expand(self, args: argparse.Namespace, config_file: str) -> Hook:
+        map_ = {
+            '%CONFIG_BASEPATH%': os.path.dirname(os.path.abspath(config_file)),
+        }
+        values = self._asdict()
+        for k, v in map_.items():
+            values['entry'] = values['entry'].replace(k, v)
+            values['args'] = [x.replace(k, v) for x in values['args']]
+        return Hook(**values)
+
 
 _KEYS = frozenset(set(Hook._fields) - {'src', 'prefix'})

tests/commands/run_test.py

@@ -265,6 +265,39 @@ def test_global_exclude(cap_out, store, in_git_dir):
     assert printed.endswith(b'\n\n.pre-commit-config.yaml\nbar.py\n\n')
 
 
+def test_global_hook_expand(cap_out, store, in_git_dir):
+    config = {
+        'repos': [
+            {
+                'repo': 'local',
+                'hooks': [
+                    {
+                        'id': 'foo',
+                        'language': 'script',
+                        'name': 'bar',
+                        'entry': '%CONFIG_BASEPATH%/script',
+                        'args': ['%CONFIG_BASEPATH%'],
+                    },
+                ],
+            },
+        ],
+    }
+    write_config('.', config)
+
+    open('foo.py', 'a').close()
+    cmd_output('git', 'add', '.')
+    opts = run_opts(verbose=False)
+    ret, printed = _do_run(cap_out, store, str(in_git_dir), opts)
+    # script doesn't exist so this needs to fail
+    assert ret != 0
+
+    # %CONFIG_BASEPATH% is properly expanded
+    assert b'%CONFIG_BASEPATH%' not in printed
+    if sys.platform != 'win32':
+        # on windows path separator would look different
+        assert f'{in_git_dir}/script'.encode() in printed
+
+
 def test_global_files(cap_out, store, in_git_dir):
     config = {
         'files': r'^bar\.py$',