Support GitHub tree URLs in getGitHubFileFetchUrl

Co-authored-by: Oliver Sand <oliver.sand@sda-se.com>
Signed-off-by: Dominik Henneke <dominik.henneke@sda-se.com>

.changeset/friendly-schools-sing.md

@@ -0,0 +1,5 @@
+---
+'@backstage/integration': patch
+---
+
+Support GitHub `tree` URLs in `getGitHubFileFetchUrl`.

packages/integration/src/github/core.test.ts

@@ -84,6 +84,36 @@ describe('github core', () => {
       );
     });
 
+    it('happy path for github tree', () => {
+      const config: GitHubIntegrationConfig = {
+        host: 'github.com',
+        apiBaseUrl: 'https://api.github.com',
+      };
+      expect(
+        getGitHubFileFetchUrl(
+          'https://github.com/a/b/tree/branchname/path/to/c.yaml',
+          config,
+        ),
+      ).toEqual(
+        'https://api.github.com/repos/a/b/contents/path/to/c.yaml?ref=branchname',
+      );
+    });
+
+    it('happy path for ghe tree', () => {
+      const config: GitHubIntegrationConfig = {
+        host: 'ghe.mycompany.net',
+        apiBaseUrl: 'https://ghe.mycompany.net/api/v3',
+      };
+      expect(
+        getGitHubFileFetchUrl(
+          'https://ghe.mycompany.net/a/b/tree/branchname/path/to/c.yaml',
+          config,
+        ),
+      ).toEqual(
+        'https://ghe.mycompany.net/api/v3/repos/a/b/contents/path/to/c.yaml?ref=branchname',
+      );
+    });
+
     it('happy path for github raw', () => {
       const config: GitHubIntegrationConfig = {
         host: 'github.com',

packages/integration/src/github/core.ts

@@ -39,7 +39,11 @@ export function getGitHubFileFetchUrl(
       !owner ||
       !name ||
       !ref ||
-      (filepathtype !== 'blob' && filepathtype !== 'raw')
+      // GitHub is automatically redirecting tree urls to blob urls so it's
+      // fine to pass a tree url.
+      (filepathtype !== 'blob' &&
+        filepathtype !== 'raw' &&
+        filepathtype !== 'tree')
     ) {
       throw new Error('Invalid GitHub URL or file path');
     }