feat(cli): add pull request creation with AI-generated messages (#2)

Add a new `gai pr` subcommand that generates pull request titles and descriptions using AI, then creates the PR via GitHub CLI (`gh`) or Gitea CLI (`tea`). This extends the existing commit-generation system by reusing retry logic and prompt infrastructure, and introduces a `callAI` function that returns raw output (instead of pre-cleaned messages) to support structured PR responses.

Reviewed-on: #2

src/pr.ts

@@ -0,0 +1,184 @@
+export type Platform = "github" | "gitea";
+
+export async function getDefaultBranch(): Promise<string> {
+  try {
+    const result =
+      await Bun.$`git symbolic-ref refs/remotes/origin/HEAD`.quiet().text();
+    return result.trim().replace("refs/remotes/origin/", "");
+  } catch {
+    try {
+      const branches = await Bun.$`git branch -r`.quiet().text();
+      for (const line of branches.split("\n")) {
+        const trimmed = line.trim();
+        if (trimmed === "origin/main" || trimmed === "origin/master") {
+          return trimmed.replace("origin/", "");
+        }
+      }
+    } catch {}
+    return "main";
+  }
+}
+
+export async function getBranchName(): Promise<string> {
+  const result =
+    await Bun.$`git rev-parse --abbrev-ref HEAD`.quiet().text();
+  return result.trim();
+}
+
+export async function getBranchCommits(base: string): Promise<string[]> {
+  try {
+    const result =
+      await Bun.$`git log --oneline origin/${base}..HEAD`.quiet().text();
+    return result.trim().split("\n").filter(Boolean);
+  } catch {
+    try {
+      const result =
+        await Bun.$`git log --oneline ${base}..HEAD`.quiet().text();
+      return result.trim().split("\n").filter(Boolean);
+    } catch {
+      return [];
+    }
+  }
+}
+
+export async function getBranchDiff(base: string): Promise<string> {
+  try {
+    const result =
+      await Bun.$`git diff ${base}...HEAD`.quiet().text();
+    return result.trim();
+  } catch {
+    return "";
+  }
+}
+
+function parseRemoteHostname(url: string): string | null {
+  const hostname = url
+    .trim()
+    .toLowerCase()
+    .replace(/^(https?:\/\/|ssh:\/\/|git:\/\/)/, "")
+    .replace(/^[^@]+@/, "")
+    .split(/[:/]/)[0];
+  return hostname || null;
+}
+
+export async function detectPlatform(): Promise<Platform | null> {
+  try {
+    const url = await Bun.$`git remote get-url origin`.quiet().text();
+    const hostname = parseRemoteHostname(url);
+
+    if (!hostname) return null;
+
+    if (hostname === "github.com") return "github";
+    if (hostname.includes("gitea")) return "gitea";
+    return null;
+  } catch {
+    return null;
+  }
+}
+
+export async function getRemoteHostname(): Promise<string | null> {
+  try {
+    const url = await Bun.$`git remote get-url origin`.quiet().text();
+    return parseRemoteHostname(url);
+  } catch {
+    return null;
+  }
+}
+
+export function checkCLI(platform: Platform): string | null {
+  const bin = platform === "github" ? "gh" : "tea";
+  const path = Bun.which(bin);
+  if (!path) {
+    if (platform === "github") {
+      return "GitHub CLI (gh) not found. Install: brew install gh";
+    }
+    return "Gitea CLI (tea) not found. Install from: https://gitea.com/gitea/tea";
+  }
+  return null;
+}
+
+export async function checkAuth(platform: Platform): Promise<string | null> {
+  if (platform === "github") {
+    try {
+      await Bun.$`gh auth status`.quiet();
+      return null;
+    } catch {
+      return "Not authenticated with GitHub CLI. Run: gh auth login";
+    }
+  }
+
+  try {
+    const result = await Bun.$`tea logins list`.quiet().text();
+    if (result.trim()) return null;
+    return "Not authenticated with Gitea CLI. Run: tea login add";
+  } catch {
+    return "Not authenticated with Gitea CLI. Run: tea login add";
+  }
+}
+
+export async function createPR(
+  platform: Platform,
+  title: string,
+  body: string,
+  base: string,
+  draft: boolean,
+): Promise<string> {
+  if (platform === "github") {
+    const args = [
+      "pr",
+      "create",
+      "--title",
+      title,
+      "--body",
+      body,
+      "--base",
+      base,
+    ];
+    if (draft) args.push("--draft");
+
+    const proc = Bun.spawn(["gh", ...args], {
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    const exitCode = await proc.exited;
+    const stdout = await new Response(proc.stdout).text();
+    const stderr = await new Response(proc.stderr).text();
+
+    if (exitCode !== 0) {
+      throw new Error(
+        stderr.trim() || `gh pr create failed (exit code ${exitCode})`,
+      );
+    }
+
+    const match = stdout.match(/(https?:\/\/[^\s]+)/);
+    return match ? match[1] : stdout.trim();
+  }
+
+  const args = [
+    "pulls",
+    "create",
+    "--title",
+    title,
+    "--description",
+    body,
+    "--base",
+    base,
+  ];
+
+  const proc = Bun.spawn(["tea", ...args], {
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+  const exitCode = await proc.exited;
+  const stdout = await new Response(proc.stdout).text();
+  const stderr = await new Response(proc.stderr).text();
+
+  if (exitCode !== 0) {
+    throw new Error(
+      stderr.trim() || `tea pulls create failed (exit code ${exitCode})`,
+    );
+  }
+
+  const match = stdout.match(/(https?:\/\/[^\s]+)/);
+  return match ? match[1] : stdout.trim();
+}