cli: no longer diff dev/ or src/

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/big-jeans-love.md

@@ -0,0 +1,5 @@
+---
+'@backstage/cli': patch
+---
+
+The `plugin:diff` command no longer validates the existence of any of the files within `dev/` or `src/`.

packages/cli/src/commands/plugin/diff.ts

@@ -39,18 +39,13 @@ const fileHandlers = [
     patterns: ['package.json'],
     handler: handlers.packageJson,
   },
-  {
-    // Not all plugins have routes
-    patterns: ['src/routes.ts'],
-    handler: handlers.skip,
-  },
   {
     // make sure files in 1st level of src/ and dev/ exist
-    patterns: ['.eslintrc.js', /^(src|dev)\/[^/]+$/],
+    patterns: ['.eslintrc.js'],
     handler: handlers.exists,
   },
   {
-    patterns: ['README.md', 'tsconfig.json', /^src\//],
+    patterns: ['README.md', 'tsconfig.json', /^src\//, /^dev\//],
     handler: handlers.skip,
   },
 ];