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