Exclude some paths from .git folder removal

README.md

@@ -9,12 +9,40 @@ While not a best practice, sometimes it's simply a requirement.
 ## How to use the plugin
 
 When required in composer.json, the plugin will automatically
-search for any .git directories in installed or updated 
+search for any .git directories in installed or updated
 dependencies and delete them immediately.
 
 There's nothing else you need to do after requiring this plugin
 in your main composer.json file.
 
+Optionally, if you wish to develop on one of your project's dependencies and keep its .git folder, you can tell composer-cleanup-vcs-dirs to exclude that dependency's path from deletion. In your project's composer.json, set the `extras > cleanup-vcs-dirs > exclude` entry with a pattern that matches the dependency installation directories you wish to keep the .git folder for. For example, the following would keep .git folders located in a `custom` folder and inside the `symfony/debug` folder:
+
+```json
+{
+    "name": "my-project",
+    "description": "This is the composer.json file",
+    "type": "project",
+    "extra": {
+        "cleanup-vcs-dirs": {
+            "exclude": [
+                "symfony/debug",
+                "/custom\\/*/"
+            ]
+        }
+    }
+}
+```
+
+The `extras > cleanup-vcs-dirs > exclude` directory path can be a string or an array of strings. You can use patterns (delimited with `/` sign) or simple strings.
+
+ * `"some/special/dir"`
+ * `["some/directory", "another/directory"]`
+ * `"/some\\/special\\/dir/"`
+
+   (Note that any backslash characters in a regex string need to be escaped with an extra backslash when used in a JSON file like composer.json. In other words, PHP's `'/custom\/*/'` becomes `"/custom\\/*/"` in JSON.)
+
+After adding an `extras > cleanup-vcs-dirs > exclude` entry, you will need to run `composer reinstall --prefer-source [package-needing-git]` to force composer to re-add the .git folder.
+
 ## Running the command directly
 
 You can also run the cleanup-vcs-dirs command directly in Composer.

src/Handler.php

@@ -46,14 +46,24 @@ public function getVcsDirs($parentDir, $excludeRoot = false) {
 
     $iterator = $finder
       ->directories()
-      ->in($parentDir)
+      ->in($excludeRoot ? $parentDir : './')
       ->ignoreVCS(false)
       ->ignoreDotFiles(false)
       ->exclude(['node_modules', '.git/*'])
       ->name('.git');
 
     if ($excludeRoot) {
-      $iterator = $iterator->depth('> 0');
+      $iterator->depth('> 0');
+    }
+    else {
+      $iterator->path($parentDir);
+    }
+
+    $extra = $this->composer->getPackage()->getExtra();
+    if (isset($extra['cleanup-vcs-dirs']) && !empty($extra['cleanup-vcs-dirs']['exclude'])) {
+      foreach ((array) $extra['cleanup-vcs-dirs']['exclude'] as $pattern) {
+        $iterator->notPath($pattern);
+      }
     }
 
     return $iterator;