feat(hooks): Validate Mergify configuration location (#4)

Ensure exactly one Mergify configuration file exists in an allowed location.

Author: JulianMaurin

.pre-commit-hooks.yaml

@@ -12,3 +12,32 @@
       | \.mergify/config\.yml
       | \.github/mergify\.yml
     )$
+
+- id: validate-mergify-config-location
+  name: Validate Mergify configuration location
+  description: Ensure exactly one Mergify configuration file exists in an allowed location
+  entry: sh -eu -c
+  language: system
+  pass_filenames: false
+  always_run: true
+  args:
+    - |
+      found=""
+      for f in \
+        .mergify.yml \
+        .mergify/config.yml \
+        .github/mergify.yml
+      do
+        [ -f "$f" ] || continue
+        if [ -z "$found" ]; then
+          found="$f"
+        else
+          printf "Multiple Mergify configuration files found. Ensure only one location is used:\n  - %s\n  - %s\n" "$found" "$f" >&2
+          exit 1
+        fi
+      done
+
+      if [ -z "$found" ]; then
+        echo "Mergify configuration missing. Expected one of: .mergify.yml, .mergify/config.yml, .github/mergify.yml" >&2
+        exit 1
+      fi

README.md

@@ -9,26 +9,36 @@ Add the following to your `.pre-commit-config.yaml`:
 ```yaml
 repos:
   - repo: https://github.com/Mergifyio/mergify-pre-commit
-    rev: 1.0.0
+    rev: 1.1.0
     hooks:
+      - id: validate-mergify-config-location
       - id: validate-mergify-config
 ```
 
-It uses `check-jsonschema` under the hood with Mergify's official schema:
+### validate-mergify-config
 
-```
-https://docs.mergify.com/mergify-configuration-schema.json
-```
+Validate Mergify configuration files against the official schema.
 
-### Customization
+- Uses `check-jsonschema` with Mergify's schema: `https://docs.mergify.com/mergify-configuration-schema.json`
+- Targets files matching the hook's `files` pattern.
 
-To pass extra arguments to `check-jsonschema`, use `args` in your config. For example, to enable verbose mode:
+Customization example (pass extra args to `check-jsonschema`):
 
 ```yaml
 repos:
   - repo: https://github.com/Mergifyio/mergify-pre-commit
-    rev: 1.0.0
+    rev: 1.1.0
     hooks:
       - id: validate-mergify-config
         args: ["--verbose"]
 ```
+
+### validate-mergify-config-location
+
+Ensure exactly one Mergify configuration file exists in an allowed location.
+
+- Allowed locations (yml only):
+  - `.mergify.yml`
+  - `.mergify/config.yml`
+  - `.github/mergify.yml`
+- Runs as a system shell script, checks repo state (not just staged files).