feat: create a function to get the github default branch

src/lib/source-handlers/github/get-default-branch.ts

@@ -0,0 +1,22 @@
+import { Octokit } from '@octokit/rest';
+import * as debugLib from 'debug';
+import { getGithubToken } from './get-github-token';
+import { getGithubBaseUrl } from './github-base-url';
+
+const debug = debugLib('snyk:get-github-defaultBranch-script');
+
+export async function getGithubReposDefaultBranch(
+    RepoName: string,
+    host?: string,
+  ): Promise<string> {
+    const githubToken = getGithubToken();
+    const baseUrl = getGithubBaseUrl(host);
+    const octokit: Octokit = new Octokit({ baseUrl, auth: githubToken });
+
+    debug(`fetching the default branch for repo: ${RepoName}`);
+
+    const response = await octokit.request(`GET /repos/${RepoName}`)
+
+    return response.data.default_branch as string
+
+  }

src/lib/source-handlers/github/index.ts

@@ -1,4 +1,5 @@
 export * from './list-organizations';
 export * from './list-repos';
 export * from './organization-is-empty';
+export * from './get-default-branch';
 export * from './types';