cmd/go: skip git sha256 tests if git < 2.29

Fix test building on older Ubuntu LTS releases (that are still
supported). Git SHA256 support was only included in 2.29, which came out
in 2021. Check the output of `git version` and skip these tests if the
version is older than that introduction.

Thanks to @ianlancetaylor for flagging this.

Updates: #73704
Change-Id: I9d413a63fa43f34f94c274bba7f7b883c80433b6
Reviewed-on: https://go-review.googlesource.com/c/go/+/698835
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Michael Matloob <matloob@google.com>
Auto-Submit: Michael Matloob <matloob@google.com>
Reviewed-by: Ian Alexander <jitsu@google.com>

9 files changed, 112 insertions, 1 deletions

diff --git a/src/cmd/go/internal/modfetch/codehost/git_test.go b/src/cmd/go/internal/modfetch/codehost/git_test.go
index e8884abdfe..ef01810ee8 100644
--- a/src/cmd/go/internal/modfetch/codehost/git_test.go
+++ b/src/cmd/go/internal/modfetch/codehost/git_test.go
@@ -16,14 +16,18 @@ import (
 	"io/fs"
 	"log"
 	"os"
+	"os/exec"
 	"path"
 	"path/filepath"
 	"reflect"
+	"regexp"
 	"runtime"
 	"strings"
 	"sync"
 	"testing"
 	"time"
+
+	"golang.org/x/mod/semver"
 )
 
 func TestMain(m *testing.M) {
@@ -192,9 +196,29 @@ func testRepo(ctx context.Context, t *testing.T, remote string) (Repo, error) {
 	return NewRepo(ctx, vcsName, remote, false)
 }
 
+var gitVersLineExtract = regexp.MustCompile(`git version\s+([\d.]+)`)
+
+func gitVersion(t testing.TB) string {
+	gitOut, runErr := exec.Command("git", "version").CombinedOutput()
+	if runErr != nil {
+		t.Logf("failed to execute git version: %s", runErr)
+		return "v0"
+	}
+	matches := gitVersLineExtract.FindSubmatch(gitOut)
+	if len(matches) < 2 {
+		t.Logf("git version extraction regexp did not match version line: %q", gitOut)
+		return "v0"
+	}
+	return "v" + string(matches[1])
+}
+
+const minGitSHA256Vers = "v2.29"
+
 func TestTags(t *testing.T) {
 	t.Parallel()
 
+	gitVers := gitVersion(t)
+
 	type tagsTest struct {
 		repo   string
 		prefix string
@@ -204,6 +228,9 @@ func TestTags(t *testing.T) {
 	runTest := func(tt tagsTest) func(*testing.T) {
 		return func(t *testing.T) {
 			t.Parallel()
+			if tt.repo == gitsha256repo && semver.Compare(gitVers, minGitSHA256Vers) < 0 {
+				t.Skipf("git version is too old (%+v); skipping git sha256 test", gitVers)
+			}
 			ctx := testContext(t)
 
 			r, err := testRepo(ctx, t, tt.repo)
@@ -288,6 +315,8 @@ func TestTags(t *testing.T) {
 func TestLatest(t *testing.T) {
 	t.Parallel()
 
+	gitVers := gitVersion(t)
+
 	type latestTest struct {
 		repo string
 		info *RevInfo
@@ -297,6 +326,10 @@ func TestLatest(t *testing.T) {
 			t.Parallel()
 			ctx := testContext(t)
 
+			if tt.repo == gitsha256repo && semver.Compare(gitVers, minGitSHA256Vers) < 0 {
+				t.Skipf("git version is too old (%+v); skipping git sha256 test", gitVers)
+			}
+
 			r, err := testRepo(ctx, t, tt.repo)
 			if err != nil {
 				t.Fatal(err)
@@ -375,6 +408,8 @@ func TestLatest(t *testing.T) {
 func TestReadFile(t *testing.T) {
 	t.Parallel()
 
+	gitVers := gitVersion(t)
+
 	type readFileTest struct {
 		repo string
 		rev  string
@@ -387,6 +422,10 @@ func TestReadFile(t *testing.T) {
 			t.Parallel()
 			ctx := testContext(t)
 
+			if tt.repo == gitsha256repo && semver.Compare(gitVers, minGitSHA256Vers) < 0 {
+				t.Skipf("git version is too old (%+v); skipping git sha256 test", gitVers)
+			}
+
 			r, err := testRepo(ctx, t, tt.repo)
 			if err != nil {
 				t.Fatal(err)
@@ -468,6 +507,8 @@ type zipFile struct {
 func TestReadZip(t *testing.T) {
 	t.Parallel()
 
+	gitVers := gitVersion(t)
+
 	type readZipTest struct {
 		repo   string
 		rev    string
@@ -480,6 +521,10 @@ func TestReadZip(t *testing.T) {
 			t.Parallel()
 			ctx := testContext(t)
 
+			if tt.repo == gitsha256repo && semver.Compare(gitVers, minGitSHA256Vers) < 0 {
+				t.Skipf("git version is too old (%+v); skipping git sha256 test", gitVers)
+			}
+
 			r, err := testRepo(ctx, t, tt.repo)
 			if err != nil {
 				t.Fatal(err)
@@ -753,6 +798,8 @@ var hgmap = map[string]string{
 func TestStat(t *testing.T) {
 	t.Parallel()
 
+	gitVers := gitVersion(t)
+
 	type statTest struct {
 		repo string
 		rev  string
@@ -764,6 +811,10 @@ func TestStat(t *testing.T) {
 			t.Parallel()
 			ctx := testContext(t)
 
+			if tt.repo == gitsha256repo && semver.Compare(gitVers, minGitSHA256Vers) < 0 {
+				t.Skipf("git version is too old (%+v); skipping git sha256 test", gitVers)
+			}
+
 			r, err := testRepo(ctx, t, tt.repo)
 			if err != nil {
 				t.Fatal(err)
diff --git a/src/cmd/go/internal/vcweb/script.go b/src/cmd/go/internal/vcweb/script.go
index 3342ab200c..0856c40677 100644
--- a/src/cmd/go/internal/vcweb/script.go
+++ b/src/cmd/go/internal/vcweb/script.go
@@ -18,12 +18,14 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"runtime"
 	"strconv"
 	"strings"
 	"time"
 
 	"golang.org/x/mod/module"
+	"golang.org/x/mod/semver"
 	"golang.org/x/mod/zip"
 )
 
@@ -42,6 +44,7 @@ func newScriptEngine() *script.Engine {
 		return script.OnceCondition(summary, func() (bool, error) { return f(), nil })
 	}
 	add("bzr", lazyBool("the 'bzr' executable exists and provides the standard CLI", hasWorkingBzr))
+	add("git-min-vers", script.PrefixCondition("<suffix> indicates a minimum git version", hasAtLeastGitVersion))
 
 	interrupt := func(cmd *exec.Cmd) error { return cmd.Process.Signal(os.Interrupt) }
 	gracePeriod := 30 * time.Second // arbitrary
@@ -394,3 +397,25 @@ func hasWorkingBzr() bool {
 	err = exec.Command(bzr, "help").Run()
 	return err == nil
 }
+
+var gitVersLineExtract = regexp.MustCompile(`git version\s+([\d.]+)`)
+
+func gitVersion() (string, error) {
+	gitOut, runErr := exec.Command("git", "version").CombinedOutput()
+	if runErr != nil {
+		return "v0", fmt.Errorf("failed to execute git version: %w", runErr)
+	}
+	matches := gitVersLineExtract.FindSubmatch(gitOut)
+	if len(matches) < 2 {
+		return "v0", fmt.Errorf("git version extraction regexp did not match version line: %q", gitOut)
+	}
+	return "v" + string(matches[1]), nil
+}
+
+func hasAtLeastGitVersion(s *script.State, minVers string) (bool, error) {
+	gitVers, gitVersErr := gitVersion()
+	if gitVersErr != nil {
+		return false, gitVersErr
+	}
+	return semver.Compare(minVers, gitVers) <= 0, nil
+}
diff --git a/src/cmd/go/scriptconds_test.go b/src/cmd/go/scriptconds_test.go
index af9691ad2a..c87c60ad33 100644
--- a/src/cmd/go/scriptconds_test.go
+++ b/src/cmd/go/scriptconds_test.go
@@ -14,10 +14,13 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"runtime"
 	"runtime/debug"
 	"sync"
 	"testing"
+
+	"golang.org/x/mod/semver"
 )
 
 func scriptConditions(t *testing.T) map[string]script.Cond {
@@ -41,6 +44,7 @@ func scriptConditions(t *testing.T) map[string]script.Cond {
 	add("case-sensitive", script.OnceCondition("$WORK filesystem is case-sensitive", isCaseSensitive))
 	add("cc", script.PrefixCondition("go env CC = <suffix> (ignoring the go/env file)", ccIs))
 	add("git", lazyBool("the 'git' executable exists and provides the standard CLI", hasWorkingGit))
+	add("git-min-vers", script.PrefixCondition("<suffix> indicates a minimum git version", hasAtLeastGitVersion))
 	add("net", script.PrefixCondition("can connect to external network host <suffix>", hasNet))
 	add("trimpath", script.OnceCondition("test binary was built with -trimpath", isTrimpath))
 
@@ -153,6 +157,28 @@ func hasWorkingGit() bool {
 	return err == nil
 }
 
+var gitVersLineExtract = regexp.MustCompile(`git version\s+([\d.]+)`)
+
+func gitVersion() (string, error) {
+	gitOut, runErr := exec.Command("git", "version").CombinedOutput()
+	if runErr != nil {
+		return "v0", fmt.Errorf("failed to execute git version: %w", runErr)
+	}
+	matches := gitVersLineExtract.FindSubmatch(gitOut)
+	if len(matches) < 2 {
+		return "v0", fmt.Errorf("git version extraction regexp did not match version line: %q", gitOut)
+	}
+	return "v" + string(matches[1]), nil
+}
+
+func hasAtLeastGitVersion(s *script.State, minVers string) (bool, error) {
+	gitVers, gitVersErr := gitVersion()
+	if gitVersErr != nil {
+		return false, gitVersErr
+	}
+	return semver.Compare(minVers, gitVers) <= 0, nil
+}
+
 func hasWorkingBzr() bool {
 	bzr, err := exec.LookPath("bzr")
 	if err != nil {
diff --git a/src/cmd/go/testdata/script/README b/src/cmd/go/testdata/script/README
index 7724bc10ec..d4f4c47af7 100644
--- a/src/cmd/go/testdata/script/README
+++ b/src/cmd/go/testdata/script/README
@@ -399,6 +399,8 @@ The available conditions are:
 	GOOS/GOARCH supports -fuzz with instrumentation
 [git]
 	the 'git' executable exists and provides the standard CLI
+[git-min-vers:*]
+	<suffix> indicates a minimum git version
 [go-builder]
 	GO_BUILDER_NAME is non-empty
 [link]
diff --git a/src/cmd/go/testdata/script/build_git_sha256_go_get_branch.txt b/src/cmd/go/testdata/script/build_git_sha256_go_get_branch.txt
index fa5557b21e..0773e08ea5 100644
--- a/src/cmd/go/testdata/script/build_git_sha256_go_get_branch.txt
+++ b/src/cmd/go/testdata/script/build_git_sha256_go_get_branch.txt
@@ -1,5 +1,6 @@
 [short] skip
 [!git] skip
+[!git-min-vers:v2.29] skip
 
 env GOPRIVATE=vcs-test.golang.org
 
diff --git a/src/cmd/go/testdata/script/build_git_sha256_moddep.txt b/src/cmd/go/testdata/script/build_git_sha256_moddep.txt
index e5bf209d89..21a296bd3d 100644
--- a/src/cmd/go/testdata/script/build_git_sha256_moddep.txt
+++ b/src/cmd/go/testdata/script/build_git_sha256_moddep.txt
@@ -1,5 +1,6 @@
 [short] skip
 [!git] skip
+[!git-min-vers:v2.29] skip
 
 env GOPRIVATE=vcs-test.golang.org
 
diff --git a/src/cmd/go/testdata/script/mod_download_git_bareRepository_sha256.txt b/src/cmd/go/testdata/script/mod_download_git_bareRepository_sha256.txt
index 9e8dc3c015..df772f5c4b 100644
--- a/src/cmd/go/testdata/script/mod_download_git_bareRepository_sha256.txt
+++ b/src/cmd/go/testdata/script/mod_download_git_bareRepository_sha256.txt
@@ -1,5 +1,6 @@
 [short] skip
 [!git] skip
+[!git-min-vers:v2.29] skip
 
 # This is a git sha256-mode copy of mod_download_git_bareRepository
 
diff --git a/src/cmd/go/testdata/vcstest/git/gitrepo-sha256.txt b/src/cmd/go/testdata/vcstest/git/gitrepo-sha256.txt
index 81b9a71c12..15068a249e 100644
--- a/src/cmd/go/testdata/vcstest/git/gitrepo-sha256.txt
+++ b/src/cmd/go/testdata/vcstest/git/gitrepo-sha256.txt
@@ -1,3 +1,5 @@
+[!git-min-vers:v2.29] skip
+
 handle git
 
 # This is a sha256 version of gitrepo1.txt (which uses sha1 hashes)
diff --git a/src/cmd/internal/script/engine.go b/src/cmd/internal/script/engine.go
index 4607868379..05b9433d3e 100644
--- a/src/cmd/internal/script/engine.go
+++ b/src/cmd/internal/script/engine.go
@@ -55,6 +55,8 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"maps"
+	"slices"
 	"sort"
 	"strings"
 	"time"
@@ -518,7 +520,7 @@ func (e *Engine) conditionsActive(s *State, conds []condition) (bool, error) {
 		if ok {
 			impl = e.Conds[prefix]
 			if impl == nil {
-				return false, fmt.Errorf("unknown condition prefix %q", prefix)
+				return false, fmt.Errorf("unknown condition prefix %q; known: %v", prefix, slices.Collect(maps.Keys(e.Conds)))
 			}
 			if !impl.Usage().Prefix {
 				return false, fmt.Errorf("condition %q cannot be used with a suffix", prefix)