feat(git): Forgejo commit API client

Verified against the live instance: status 200, total 787 commits, first
sha 1bc0da40... 'feat(customers): lift active/inactive toggle to top of
customer form'.

src/lib/git/forgejo.ts

@@ -0,0 +1,90 @@
+import "server-only";
+
+/**
+ * Forgejo REST client, against the Gitea 1.22 API shape.
+ *
+ * Everything here is measured against the live instance rather than recalled:
+ * the pagination headers, the query parameters, and the response fields are
+ * all confirmed. See the header of the Phase 2a plan.
+ */
+
+export interface ForgejoCommit {
+  sha: string;
+  html_url: string;
+  commit: {
+    message: string;
+    author: { name: string; email: string; date: string };
+    committer: { name: string; email: string; date: string };
+  };
+  parents: Array<{ sha: string }>;
+  stats?: { total: number; additions: number; deletions: number };
+}
+
+export interface CommitPage {
+  commits: ForgejoCommit[];
+  page: number;
+  pageCount: number;
+  total: number;
+  hasMore: boolean;
+}
+
+/** Forgejo caps limit at 50 on a default install; asking for more silently caps. */
+export const PAGE_SIZE = 50;
+
+function baseUrl(): string {
+  const url = process.env.FORGEJO_URL;
+  if (!url) throw new Error("FORGEJO_URL is not set");
+  return url.replace(/\/+$/, "");
+}
+
+function headers(): HeadersInit {
+  const token = process.env.FORGEJO_TOKEN;
+  return {
+    accept: "application/json",
+    // The instance currently serves commits anonymously. Sending a token when
+    // one exists means a private repository works with no code change.
+    ...(token ? { authorization: `token ${token}` } : {}),
+  };
+}
+
+/**
+ * One page of commits, newest first.
+ *
+ * stat/files/verification are disabled: each commit otherwise carries its full
+ * file list, which for a backfill of several hundred commits is a great deal
+ * of payload for data this phase does not use.
+ */
+export async function fetchCommitPage(
+  owner: string,
+  repo: string,
+  page: number
+): Promise<CommitPage> {
+  const url =
+    `${baseUrl()}/api/v1/repos/${encodeURIComponent(owner)}/${encodeURIComponent(repo)}/commits` +
+    `?page=${page}&limit=${PAGE_SIZE}&stat=false&files=false&verification=false`;
+
+  const response = await fetch(url, { headers: headers(), cache: "no-store" });
+
+  if (!response.ok) {
+    throw new Error(
+      `Forgejo returned ${response.status} for ${owner}/${repo} page ${page}`
+    );
+  }
+
+  const commits = (await response.json()) as ForgejoCommit[];
+
+  return {
+    commits,
+    page: Number(response.headers.get("x-page") ?? page),
+    pageCount: Number(response.headers.get("x-pagecount") ?? 1),
+    total: Number(response.headers.get("x-total-count") ?? commits.length),
+    hasMore: response.headers.get("x-hasmore") === "true",
+  };
+}
+
+/** Confirms a repository exists and is readable before a backfill is started. */
+export async function repoExists(owner: string, repo: string): Promise<boolean> {
+  const url = `${baseUrl()}/api/v1/repos/${encodeURIComponent(owner)}/${encodeURIComponent(repo)}`;
+  const response = await fetch(url, { headers: headers(), cache: "no-store" });
+  return response.ok;
+}