feat: integrate tool with gitlab service (#39)

* feat: integrate tool with gitlab service

Fix https://github.com/lampajr/backporting/issues/30

src/service/git/git-util.ts

@@ -0,0 +1,39 @@
+import { GitClientType } from "@bp/service/git/git.types";
+
+const PUBLIC_GITHUB_URL = "https://github.com";
+const PUBLIC_GITHUB_API = "https://api.github.com";
+
+/**
+ * Infer the remote GIT service to interact with based on the provided 
+ * pull request URL
+ * @param prUrl provided pull request URL
+ * @returns {GitClientType}
+ */
+export const inferGitClient = (prUrl: string): GitClientType => {
+  const stdPrUrl = prUrl.toLowerCase().trim();
+
+  if (stdPrUrl.includes(GitClientType.GITHUB.toString())) {
+    return GitClientType.GITHUB;
+  } else if (stdPrUrl.includes(GitClientType.GITLAB.toString())) {
+    return GitClientType.GITLAB;
+  }
+
+  throw new Error(`Remote git service not recognized from pr url: ${prUrl}`);
+};
+
+/**
+ * Infer the host git service from the pull request url
+ * @param prUrl pull/merge request url
+ * @param apiVersion the api version, ignored in case of public github
+ * @returns api URL like https://api.github.com or https://gitlab.com/api/v4
+ */
+export const inferGitApiUrl = (prUrl: string, apiVersion = "v4"): string => {
+  const url = new URL(prUrl);
+  const baseUrl = `${url.protocol}//${url.host}`;
+  
+  if (baseUrl.includes(PUBLIC_GITHUB_URL)) {
+    return PUBLIC_GITHUB_API;
+  }
+
+  return `${baseUrl}/api/${apiVersion}`;
+};