Allow dev (#70)

Author: OskarStark

README.md

@@ -48,6 +48,15 @@ _to install dev dependencies:_
         args: analyse src/
 ```
 
+_to allow dev dependencies:_
+```diff
+      uses: docker://oskarstark/phpstan-ga
++     env:
++       ALLOW_DEV: true
+      with:
+        args: analyse src/
+```
+
 _to skip checking the platform requirements:_
 ```diff
       uses: docker://oskarstark/phpstan-ga

entrypoint.sh

@@ -20,6 +20,12 @@ fi
 
 COMPOSER_COMMAND="composer install --no-progress $NO_DEV $IGNORE_PLATFORM_REQS"
 echo "::group::$COMPOSER_COMMAND"
+
+if [ "$ALLOW_DEV" = "true" ]; then
+    composer config minimum-stability dev
+    composer config prefer-stable true
+fi
+
 $COMPOSER_COMMAND
 echo "::endgroup::"
 /composer/vendor/bin/phpstan $*