feat(infra/git): clone/fetch/push/commit/status verbs + integration tests

internal/infra/git/fetch.go

@@ -0,0 +1,16 @@
+package git
+
+import "context"
+
+// Fetch 执行 git fetch --all --prune。dir 是 main_path 或 worktree path。
+func (r *DefaultRunner) Fetch(ctx context.Context, dir string, cred *Credential) error {
+	ctx, cancel := withCtx(ctx, r.cfg.FetchTimeout)
+	defer cancel()
+	env, cleanup, err := credentialEnv(r.cfg.TmpDir, cred)
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+	_, _, err = r.exec(ctx, dir, env, "fetch", "--all", "--prune")
+	return err
+}