feat: last commit api

Author: wavim

src/api/last-commit.ts

@@ -0,0 +1,31 @@
+import { readFile } from "node:fs/promises";
+import { join } from "node:path";
+
+export async function lastCommit(repo: string, head: string): Promise<string> {
+const headRefPath = join(repo, ".git", "refs", "heads", head);
+
+try {
+const hash = await readFile(headRefPath, "utf8");
+
+return hash.trimEnd();
+} catch {
+/* empty */
+}
+
+const packRefs = join(repo, ".git", "packed-refs");
+try {
+const refs = await readFile(packRefs, "utf8");
+
+for (const line of refs.split("\n")) {
+const [hash, rf = undefined] = line.split(" ");
+
+if (`refs/heads/${head}` === rf) {
+return hash;
+}
+}
+} catch {
+/* empty */
+}
+
+throw new Error("cannot get branch info");
+}

src/index.ts

@@ -2,6 +2,7 @@ export { diffCommits } from "./api/diff-commits";
 export { findParents } from "./api/find-parents";
 export { getBranches } from "./api/get-branches";
 export { headBranch } from "./api/head-branch";
+export { lastCommit } from "./api/last-commit";
 export { mergeBases } from "./api/merge-bases";
 export { readCommit } from "./api/read-object";
 export { searchRepo } from "./api/search-repo";