[plugins/catalog-backend-module-github] Throw on invalid branch name

Signed-off-by: Luke Albao <luke.albao@webflow.com>

.changeset/clear-pigs-share.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-catalog-backend-module-github': minor
+---
+
+Explicitly rejects branch names containing a slash character

plugins/catalog-backend-module-github/src/providers/GithubEntityProviderConfig.test.ts

@@ -311,4 +311,24 @@ describe('readProviderConfigs', () => {
 
     expect(() => readProviderConfigs(config)).toThrow();
   });
+
+  it('throws an error when filters.branch contains a slash', () => {
+    const config = new ConfigReader({
+      catalog: {
+        providers: {
+          github: {
+            invalidBranchUser: {
+              organization: 'test-org',
+              catalogPath: '/*/catalog-info.yaml',
+              filters: {
+                branch: 'test/a',
+              },
+            },
+          },
+        },
+      },
+    });
+
+    expect(() => readProviderConfigs(config)).toThrow();
+  });
 });

plugins/catalog-backend-module-github/src/providers/GithubEntityProviderConfig.ts

@@ -104,6 +104,12 @@ function readProviderConfig(
     );
   }
 
+  if (branchPattern?.includes('/')) {
+    throw new Error(
+      'Error while processing GitHub provider config. Slash characters (/) are not allowed in filters.branch',
+    );
+  }
+
   const schedule = config.has('schedule')
     ? readSchedulerServiceTaskScheduleDefinitionFromConfig(
         config.getConfig('schedule'),