Fix git updater for other branches (#1915)

src/main/updater/git.ts

@@ -49,7 +49,9 @@ async function getRepo() {
 async function calculateGitChanges() {
     await git("fetch");
 
-    const res = await git("log", "HEAD...origin/main", "--pretty=format:%an/%h/%s");
+    const branch = await git("branch", "--show-current");
+
+    const res = await git("log", `HEAD...origin/${branch}`, "--pretty=format:%an/%h/%s");
 
     const commits = res.stdout.trim();
     return commits ? commits.split("\n").map(line => {