Inject GitHub host to be able to clone from another GitHub instance (#922)

* Adding the ability to specify the GitHub Server URL and allowing for it to differ from the Actions workflow host

* Adding tests for injecting the GitHub URL

* Addressing code review comments for PR #922

src/input-helper.ts

@@ -125,5 +125,10 @@ export async function getInputs(): Promise<IGitSourceSettings> {
   // Set safe.directory in git global config.
   result.setSafeDirectory =
     (core.getInput('set-safe-directory') || 'true').toUpperCase() === 'TRUE'
+
+  // Determine the GitHub URL that the repository is being hosted from
+  result.githubServerUrl = core.getInput('github-server-url')
+  core.debug(`GitHub Host URL = ${result.githubServerUrl}`)
+
   return result
 }