Add PHPStan

Add Composer scripts for checking the code with PHPStan (while using
a baseline) and for updating the baseline.

When we fix PHPStan-reported issues (or update the PHPStan configuration),
we can update the baseline bit by bit until all issues are fixes.

Author: oliverklee

.gitattributes

@@ -4,5 +4,7 @@
 /.phive/
 /Doxyfile export-ignore
 /phpcs.xml export-ignore
+/phpstan-baseline.neon
+/phpstan.neon export-ignore
 /phpunit.xml export-ignore
 /tests export-ignore

.phive/phars.xml

@@ -2,4 +2,5 @@
 <phive xmlns="https://phar.io/phive">
   <phar name="phpcbf" version="^3.6.0" location="./.phive/phpcbf.phar" copy="false" installed="3.6.0"/>
   <phar name="phpcs" version="^3.6.0" location="./.phive/phpcs.phar" copy="false" installed="3.6.0"/>
+  <phar name="phpstan" version="^0.12.85" installed="0.12.85" location="./.phive/phpstan.phar" copy="false"/>
 </phive>

composer.json

@@ -23,12 +23,15 @@
             "@ci:static"
         ],
         "ci:php:sniff": "@php ./.phive/phpcs.phar lib tests",
+        "ci:php:stan": "@php ./.phive/phpstan.phar",
         "ci:static": [
-            "@ci:php:sniff"
+            "@ci:php:sniff",
+            "@ci:php:stan"
         ],
         "fix:php": [
             "@fix:php:sniff"
         ],
-        "fix:php:sniff": "@php ./.phive/phpcbf.phar lib tests"
+        "fix:php:sniff": "@php ./.phive/phpcbf.phar lib tests",
+        "phpstan:baseline": "@php ./.phive/phpstan.phar --generate-baseline"
     }
 }