fix!: use the git CLI for action clones and make builtin:checkout match actions/checkout (#1277)

The runner now uses the `git` command line instead of go-git to download actions and reusable workflows. go-git had recurring bugs and does not support SHA-256 repositories, and full clones of actions are several times faster.

`builtin:checkout` now runs `git` where the job runs and behaves like `actions/checkout`:

1. A branch is checked out as a local branch tracking `origin`, tag and pull request runs keep their ref, and a triggering tag that moved fails the step.
1. Later steps can fetch and push with the persisted token or SSH key.
1. It supports the `ssh-*`, `lfs`, `submodules`, `sparse-checkout`, `filter`, `fetch-tags`, `clean`, `persist-credentials`, `show-progress` and `set-safe-directory` inputs and the `ref` and `commit` outputs.
1. SHA-256 repositories work for actions, reusable workflows and `builtin:checkout`.

Git keeps the token off its command line, ignores `GIT_DIR` and similar variables inherited by the runner, and keeps action files LF regardless of `core.autocrlf`. A cancelled job lets git remove its lock files.

This is a breaking change: the runner needs Git 2.34.1 or newer on its `PATH`, and so do job images that use `builtin:checkout`. The official runner images include it.

Fixes: https://gitea.com/gitea/runner/issues/1077
Fixes: https://gitea.com/gitea/runner/issues/1267
Fixes: https://gitea.com/gitea/runner/issues/1279
Fixes: https://gitea.com/gitea/runner/issues/1284
Fixes: https://gitea.com/gitea/runner/issues/1285
Co-authored-by: silverwind <[email protected]>
Co-authored-by: silverwind <[email protected]>
Co-authored-by: Lunny Xiao <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1277
Reviewed-by: Lunny Xiao <[email protected]>
Reviewed-by: silverwind <[email protected]>
Co-authored-by: bircni <[email protected]>

e2e/checkout_test.go

@@ -0,0 +1,22 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+//go:build e2e
+
+package e2e
+
+import "testing"
+
+func testBuiltinCheckout(t *testing.T) {
+	t.Parallel()
+
+	api, repo := newScenario(t)
+	pushWorkflow(t, api, repo, "checkout.yml")
+	branchRun := waitForRun(t, api, repo)
+	if err := api.CreateTag(t.Context(), repo, "v1"); err != nil {
+		t.Fatalf("create tag: %v", err)
+	}
+	tagRun := waitForRunAfter(t, api, repo, branchRun.ID)
+	requireSuccess(t, api, repo, branchRun.ID)
+	requireSuccess(t, api, repo, tagRun.ID)
+}

e2e/compatibility_test.go

@@ -30,6 +30,7 @@ func TestCompatibility(t *testing.T) {
 	t.Run("artifact", testArtifactRoundTrip)
 	t.Run("cancellation_and_log_streaming", testRunCancellation)
 	t.Run("dispatch", testWorkflowDispatch)
+	t.Run("builtin_checkout", testBuiltinCheckout)
 	t.Run("ephemeral", testEphemeralRunner)
 	t.Run("kubernetes", testKubernetes)
 }

e2e/gitea_api.go

@@ -53,6 +53,12 @@ func (a *GiteaAPI) CreateFile(ctx context.Context, repo, path, content, message
 	return a.doJSON(ctx, http.MethodPost, url, body, nil)
 }
 
+func (a *GiteaAPI) CreateTag(ctx context.Context, repo, name string) error {
+	body := map[string]any{"tag_name": name}
+	url := fmt.Sprintf("/api/v1/repos/%s/%s/tags", giteaAdminUser, repo)
+	return a.doJSON(ctx, http.MethodPost, url, body, nil)
+}
+
 func (a *GiteaAPI) CreateSecret(ctx context.Context, repo, name, value string) error {
 	body := map[string]any{"data": value}
 	url := fmt.Sprintf("/api/v1/repos/%s/%s/actions/secrets/%s", giteaAdminUser, repo, name)

e2e/gitea_fixture.go

@@ -188,6 +188,7 @@ func StartGitea(ctx context.Context, cli mobyclient.APIClient) (*GiteaFixture, e
 				"GITEA__security__INSTALL_LOCK=true",
 				"GITEA__database__DB_TYPE=sqlite3",
 				"GITEA__actions__ENABLED=true",
+				"GITEA__server__LFS_START_SERVER=true",
 				"GITEA__server__ROOT_URL=" + baseURL + "/",
 			},
 			ExposedPorts: network.PortSet{containerPort: struct{}{}},

e2e/main_test.go

@@ -141,6 +141,11 @@ func dumpRunLogs(t *testing.T, api *GiteaAPI, repo string, runID int64) {
 }
 
 func waitForRun(t *testing.T, api *GiteaAPI, repo string) *ActionRun {
+	t.Helper()
+	return waitForRunAfter(t, api, repo, 0)
+}
+
+func waitForRunAfter(t *testing.T, api *GiteaAPI, repo string, previousID int64) *ActionRun {
 	t.Helper()
 	ctx, cancel := context.WithTimeout(t.Context(), time.Minute)
 	defer cancel()
@@ -150,7 +155,7 @@ func waitForRun(t *testing.T, api *GiteaAPI, repo string) *ActionRun {
 		if err != nil {
 			t.Fatalf("get latest run: %v", err)
 		}
-		if len(runs) > 0 {
+		if len(runs) > 0 && runs[0].ID > previousID {
 			return &runs[0]
 		}
 		select {

e2e/testdata/workflows/checkout.yml

@@ -0,0 +1,61 @@
+name: checkout
+on: push
+jobs:
+  checkout:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - id: checkout
+        uses: builtin:checkout
+      - uses: builtin:checkout
+        with:
+          ref: ${{ github.ref_name }}
+          path: short
+      - run: test "$(git -C short rev-parse HEAD)" = "$GITHUB_SHA"
+      - if: github.ref_type == 'branch'
+        run: |
+          test "$(git symbolic-ref HEAD)" = "$GITHUB_REF"
+          test "${{ steps.checkout.outputs.ref }}" = "$GITHUB_REF"
+          test "${{ steps.checkout.outputs.commit }}" = "$GITHUB_SHA"
+          git -c user.name=e2e -c [email protected] commit --allow-empty -m pushed
+          git push
+          git tag moved
+          git push --force origin moved
+          git switch --orphan child
+          echo child > child.txt
+          git add child.txt
+          git -c user.name=e2e -c [email protected] commit -m child
+          git push origin child
+          git switch -c content main
+          git submodule add -b child "../${{ github.event.repository.name }}.git" sub
+          git lfs install --local
+          git lfs track '*.bin'
+          mkdir keep drop
+          echo big > keep/big.bin
+          echo big > drop/big.bin
+          git add .gitattributes keep drop
+          git -c user.name=e2e -c [email protected] commit -m content
+          git push origin content
+      - if: github.ref_type == 'branch'
+        uses: builtin:checkout
+        with:
+          ref: content
+          path: full
+          submodules: true
+          lfs: true
+      - if: github.ref_type == 'branch'
+        uses: builtin:checkout
+        with:
+          ref: content
+          path: sparse
+          sparse-checkout: keep
+          lfs: true
+      - if: github.ref_type == 'branch'
+        run: |
+          test "$(cat full/sub/child.txt)" = child
+          test "$(cat full/keep/big.bin)" = big
+          test "$(cat sparse/keep/big.bin)" = big
+          test ! -e sparse/drop
+      - if: github.ref_type == 'tag'
+        run: test "$(git describe --tags)" = "$GITHUB_REF_NAME"