buildx: install release binaries from a fork

adds a new API method that uses the github releases API
to find the appropriate version to download.

Signed-off-by: Nick Santos <nick.santos@docker.com>

__tests__/buildx/install.test.ts

@@ -19,9 +19,12 @@ import * as fs from 'fs';
 import * as path from 'path';
 import * as rimraf from 'rimraf';
 import osm = require('os');
+import * as github from '@actions/github';
 
 import {Install} from '../../src/buildx/install';
 
+const release_0_11_0 = require('./release-v0.11.0.json');
+
 // prettier-ignore
 const tmpDir = path.join(process.env.TEMP || '/tmp', 'buildx-jest');
 
@@ -105,6 +108,22 @@ describe('build', () => {
   }, 100000);
 });
 
+describe('installReleaseFromFork', () => {
+  it('installs v0.11.0 by querying github releases', async () => {
+    jest.spyOn(github, 'getOctokit').mockImplementation(() => {
+      const request = () => Promise.resolve({data: release_0_11_0});
+
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      return {request} as any;
+    });
+    const install = new Install();
+    const toolPath = await install.installReleaseFromFork('https://github.com/docker/buildx.git#v0.11.0');
+    expect(fs.existsSync(toolPath)).toBe(true);
+    const buildxBin = await install.installStandalone(toolPath, tmpDir);
+    expect(fs.existsSync(buildxBin)).toBe(true);
+  }, 100000);
+});
+
 describe('getRelease', () => {
   it('returns latest buildx GitHub release', async () => {
     const release = await Install.getRelease('latest');