Anchor dependency preparation to checkout root

preparation_test.go

@@ -249,6 +249,65 @@ func TestPrepareBuildDependenciesUsesSelectedModuleDirectory(t *testing.T) {
 	}
 }
 
+func TestPrepareBuildDependenciesSelectsFromCheckoutRoot(t *testing.T) {
+	repo := t.TempDir()
+	buildGit(t, repo, "init")
+	nested := filepath.Join(repo, "nested")
+	child := filepath.Join(nested, "child")
+	if err := os.MkdirAll(child, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink("nested/child", filepath.Join(repo, "link")); err != nil {
+		t.Fatal(err)
+	}
+	bin := t.TempDir()
+	marker := filepath.Join(t.TempDir(), "directory")
+	if err := os.WriteFile(filepath.Join(bin, "go"), []byte("#!/bin/sh\nprintf '%s' \"$PWD\" > \"$PREPARE_DIR_MARKER\"\n"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("PATH", bin+string(os.PathListSeparator)+os.Getenv("PATH"))
+	t.Setenv("PREPARE_DIR_MARKER", marker)
+	for _, tc := range []struct{ dir, module, want string }{
+		{repo, "", repo}, {child, "", repo}, {repo, "nested", nested},
+		{child, "nested", nested}, {child, "link/..", nested},
+	} {
+		err := releasekit.PrepareBuildDependencies(context.Background(), releasekit.DependencyPreparationRequest{RepositoryDir: tc.dir, ModuleDir: tc.module})
+		got, readErr := os.ReadFile(marker)
+		if err != nil || readErr != nil || string(got) != tc.want {
+			t.Fatalf("selection %q, %q = %q, error %v, read %v; want %q", tc.dir, tc.module, got, err, readErr, tc.want)
+		}
+	}
+}
+
+func TestPrepareBuildDependenciesWithoutGit(t *testing.T) {
+	repo := t.TempDir()
+	buildGit(t, repo, "init")
+	standalone := t.TempDir()
+	bin := t.TempDir()
+	marker := filepath.Join(t.TempDir(), "go-ran")
+	if err := os.WriteFile(filepath.Join(bin, "go"), []byte("#!/bin/sh\nprintf ran > \"$PREPARE_DIR_MARKER\"\n"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("PATH", bin)
+	t.Setenv("PREPARE_DIR_MARKER", marker)
+	if err := releasekit.PrepareBuildDependencies(context.Background(), releasekit.DependencyPreparationRequest{RepositoryDir: standalone}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(marker); err != nil {
+		t.Fatalf("Go did not run: %v", err)
+	}
+	if err := os.Remove(marker); err != nil {
+		t.Fatal(err)
+	}
+	err := releasekit.PrepareBuildDependencies(context.Background(), releasekit.DependencyPreparationRequest{RepositoryDir: repo})
+	if !errors.Is(err, exec.ErrNotFound) {
+		t.Fatalf("checkout error = %v, want missing Git", err)
+	}
+	if _, err := os.Stat(marker); !os.IsNotExist(err) {
+		t.Fatalf("Go ran after discovery failure: %v", err)
+	}
+}
+
 func publishPreparationTag(t *testing.T, repository string) string {
 	t.Helper()
 	return publishPreparationTagNamed(t, repository, "v1.2.3")