fix: matrix-job data races + outputs, leaner offline test suite (#994)

Running the full suite under `-race` (dropping `-short`) exposed pre-existing data races in parallel matrix-job execution, fixed by not sharing mutable state across combinations:

- `containerDaemonSocket()`/`validVolumes()` derive per-job values instead of mutating shared `Config`
- `getWorkflowSecrets` builds a fresh map, `rc.steps()` clones each step, and go-git workdir access is serialized
- every write to a shared `Job`'s result/outputs runs under a per-`Job` lock, each combo interpolating outputs from a pristine snapshot (last wins, as on GitHub)

### Test suite

- capability gates (docker / network / host-tools / Linux) replace the `-short` skips, and the suite runs offline via local fixtures (the artifact flow uses an in-process loopback server, only the docker-action force-pull needs the network)
- drops redundant tests, adds a regression test for https://gitea.com/gitea/runner/issues/981 and a docker-in-docker harness (`make test-dind`)

---
This PR was written with the help of Claude Opus 4.7

Reviewed-on: https://gitea.com/gitea/runner/pulls/994
Reviewed-by: Nicolas <bircni@icloud.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

act/common/git/git.go

@@ -66,8 +66,21 @@ func (e *Error) Commit() string {
 	return e.commit
 }
 
+// goGitMu serializes go-git repository access across the process. go-git is not safe for
+// concurrent use of the same repository (even read access decodes packfiles into shared
+// state), so parallel jobs inspecting the shared workdir repo race without this. The guarded
+// operations are fast local reads; gitea runs one job per process, so the lock is effectively
+// uncontended in production.
+var goGitMu sync.Mutex
+
 // FindGitRevision get the current git revision
 func FindGitRevision(ctx context.Context, file string) (shortSha, sha string, err error) {
+	goGitMu.Lock()
+	defer goGitMu.Unlock()
+	return findGitRevision(ctx, file)
+}
+
+func findGitRevision(ctx context.Context, file string) (shortSha, sha string, err error) {
 	logger := common.Logger(ctx)
 
 	gitDir, err := git.PlainOpenWithOptions(
@@ -99,10 +112,13 @@ func FindGitRevision(ctx context.Context, file string) (shortSha, sha string, er
 
 // FindGitRef get the current git ref
 func FindGitRef(ctx context.Context, file string) (string, error) {
+	goGitMu.Lock()
+	defer goGitMu.Unlock()
+
 	logger := common.Logger(ctx)
 
 	logger.Debugf("Loading revision from git directory")
-	_, ref, err := FindGitRevision(ctx, file)
+	_, ref, err := findGitRevision(ctx, file)
 	if err != nil {
 		return "", err
 	}
@@ -174,6 +190,8 @@ func FindGitRef(ctx context.Context, file string) (string, error) {
 
 // FindGithubRepo get the repo
 func FindGithubRepo(ctx context.Context, file, githubInstance, remoteName string) (string, error) {
+	goGitMu.Lock()
+	defer goGitMu.Unlock()
 	if remoteName == "" {
 		remoteName = "origin"
 	}

act/common/git/git_test.go

@@ -16,7 +16,6 @@ import (
 	"testing"
 	"time"
 
-	log "github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -50,10 +49,6 @@ func TestFindGitSlug(t *testing.T) {
 	}
 }
 
-func testDir(t *testing.T) string {
-	return t.TempDir()
-}
-
 func cleanGitHooks(dir string) error {
 	hooksDir := filepath.Join(dir, ".git", "hooks")
 	files, err := os.ReadDir(hooksDir)
@@ -78,8 +73,7 @@ func cleanGitHooks(dir string) error {
 func TestFindGitRemoteURL(t *testing.T) {
 	assert := assert.New(t)
 
-	basedir := testDir(t)
-	gitConfig()
+	basedir := t.TempDir()
 	err := gitCmd("init", basedir)
 	assert.NoError(err) //nolint:testifylint // pre-existing issue from nektos/act
 	err = cleanGitHooks(basedir)
@@ -102,8 +96,7 @@ func TestFindGitRemoteURL(t *testing.T) {
 }
 
 func TestGitFindRef(t *testing.T) {
-	basedir := testDir(t)
-	gitConfig()
+	basedir := t.TempDir()
 
 	for name, tt := range map[string]struct {
 		Prepare func(t *testing.T, dir string)
@@ -180,36 +173,55 @@ func TestGitFindRef(t *testing.T) {
 }
 
 func TestGitCloneExecutor(t *testing.T) {
+	// Build a local bare "remote" so this runs offline and fast. The cases below mirror
+	// the tag/branch/sha/short-sha ref paths the executor handles, formerly exercised by
+	// cloning actions/checkout and anchore/scan-action over the network.
+	remoteDir := t.TempDir()
+	require.NoError(t, gitCmd("init", "--bare", "--initial-branch=main", remoteDir))
+
+	workDir := t.TempDir()
+	require.NoError(t, gitCmd("clone", remoteDir, workDir))
+	require.NoError(t, gitCmd("-C", workDir, "checkout", "-b", "main"))
+	require.NoError(t, gitCmd("-C", workDir, "commit", "--allow-empty", "-m", "initial"))
+	require.NoError(t, gitCmd("-C", workDir, "tag", "v2"))
+	require.NoError(t, gitCmd("-C", workDir, "push", "-u", "origin", "main"))
+	require.NoError(t, gitCmd("-C", workDir, "push", "origin", "v2"))
+
+	// A branch with a dash in the name (mirrors the historical scan-action@act-fails case).
+	require.NoError(t, gitCmd("-C", workDir, "checkout", "-b", "act-fails"))
+	require.NoError(t, gitCmd("-C", workDir, "commit", "--allow-empty", "-m", "branch-commit"))
+	require.NoError(t, gitCmd("-C", workDir, "push", "origin", "act-fails"))
+
+	out, err := exec.Command("git", "-C", workDir, "rev-parse", "main").Output()
+	require.NoError(t, err)
+	fullSha := strings.TrimSpace(string(out))
+
 	for name, tt := range map[string]struct {
-		Err      error
-		URL, Ref string
+		Err error
+		Ref string
 	}{
 		"tag": {
 			Err: nil,
-			URL: "https://github.com/actions/checkout",
 			Ref: "v2",
 		},
 		"branch": {
 			Err: nil,
-			URL: "https://github.com/anchore/scan-action",
 			Ref: "act-fails",
 		},
 		"sha": {
 			Err: nil,
-			URL: "https://github.com/actions/checkout",
-			Ref: "5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f", // v2
+			Ref: fullSha,
 		},
 		"short-sha": {
-			Err: &Error{ErrShortRef, "5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f"},
-			URL: "https://github.com/actions/checkout",
-			Ref: "5a4ac90", // v2
+			Err: &Error{ErrShortRef, fullSha},
+			Ref: fullSha[:7],
 		},
 	} {
 		t.Run(name, func(t *testing.T) {
 			clone := NewGitCloneExecutor(NewGitCloneExecutorInput{
-				URL: tt.URL,
+				URL: remoteDir,
 				Ref: tt.Ref,
-				Dir: testDir(t),
+				Dir: t.TempDir(),
 			})
 
 			err := clone(context.Background())
@@ -228,8 +240,6 @@ func TestGitCloneExecutorNonFastForwardRef(t *testing.T) {
 	// non-fast-forward between two fetches. Before the fix, the fetch used Force=false,
 	// causing go-git to return ErrForceNeeded and short-circuit the checkout.
 
-	gitConfig()
-
 	// Create a bare "remote" repo with an initial commit on main and a feature branch.
 	remoteDir := t.TempDir()
 	require.NoError(t, gitCmd("init", "--bare", "--initial-branch=main", remoteDir))
@@ -280,8 +290,6 @@ func TestGitCloneExecutorNonFastForwardRef(t *testing.T) {
 }
 
 func TestGitCloneExecutorOfflineMode(t *testing.T) {
-	gitConfig()
-
 	// Build a local "remote" with a single commit on main.
 	remoteDir := t.TempDir()
 	require.NoError(t, gitCmd("init", "--bare", "--initial-branch=main", remoteDir))
@@ -327,22 +335,21 @@ func TestGitCloneExecutorOfflineMode(t *testing.T) {
 	})
 }
 
-func gitConfig() {
-	if os.Getenv("GITHUB_ACTIONS") == "true" {
-		var err error
-		if err = gitCmd("config", "--global", "user.email", "test@test.com"); err != nil {
-			log.Error(err)
-		}
-		if err = gitCmd("config", "--global", "user.name", "Unit Test"); err != nil {
-			log.Error(err)
-		}
-	}
-}
-
 func gitCmd(args ...string) error {
 	cmd := exec.Command("git", args...)
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
+	// Inject a deterministic identity and ignore the host's global/system config so commits
+	// succeed regardless of the host having no user.name/user.email (e.g. CI, GITHUB_ACTIONS
+	// unset) or a global commit.gpgsign, and without mutating the developer's ~/.gitconfig.
+	cmd.Env = append(os.Environ(),
+		"GIT_AUTHOR_NAME=Unit Test",
+		"GIT_AUTHOR_EMAIL=test@test.com",
+		"GIT_COMMITTER_NAME=Unit Test",
+		"GIT_COMMITTER_EMAIL=test@test.com",
+		"GIT_CONFIG_GLOBAL=/dev/null",
+		"GIT_CONFIG_SYSTEM=/dev/null",
+	)
 
 	err := cmd.Run()
 	if exitError, ok := err.(*exec.ExitError); ok {