Refactor git version functions and check compatibility (go-gitea#29155)

Introduce a new function checkGitVersionCompatibility, when the git
version can't be used by Gitea, tell the end users to downgrade or
upgrade. The refactored functions are related to make the code easier to
test.

And simplify the comments for "safe.directory"

---------

Co-authored-by: delvh <[email protected]>

modules/git/git.go

@@ -39,36 +39,37 @@ var (
 	gitVersion *version.Version
 )
 
-// loadGitVersion returns current Git version from shell. Internal usage only.
-func loadGitVersion() (*version.Version, error) {
+// loadGitVersion tries to get the current git version and stores it into a global variable
+func loadGitVersion() error {
 	// doesn't need RWMutex because it's executed by Init()
 	if gitVersion != nil {
-		return gitVersion, nil
+		return nil
 	}
 
 	stdout, _, runErr := NewCommand(DefaultContext, "version").RunStdString(nil)
 	if runErr != nil {
-		return nil, runErr
+		return runErr
 	}
 
-	fields := strings.Fields(stdout)
-	if len(fields) < 3 {
-		return nil, fmt.Errorf("invalid git version output: %s", stdout)
+	ver, err := parseGitVersionLine(strings.TrimSpace(stdout))
+	if err == nil {
+		gitVersion = ver
 	}
+	return err
+}
 
-	var versionString string
-
-	// Handle special case on Windows.
-	i := strings.Index(fields[2], "windows")
-	if i >= 1 {
-		versionString = fields[2][:i-1]
-	} else {
-		versionString = fields[2]
+func parseGitVersionLine(s string) (*version.Version, error) {
+	fields := strings.Fields(s)
+	if len(fields) < 3 {
+		return nil, fmt.Errorf("invalid git version: %q", s)
 	}
 
-	var err error
-	gitVersion, err = version.NewVersion(versionString)
-	return gitVersion, err
+	// version string is like: "git version 2.29.3" or "git version 2.29.3.windows.1"
+	versionString := fields[2]
+	if pos := strings.Index(versionString, "windows"); pos >= 1 {
+		versionString = versionString[:pos-1]
+	}
+	return version.NewVersion(versionString)
 }
 
 // SetExecutablePath changes the path of git executable and checks the file permission and version.
@@ -83,8 +84,7 @@ func SetExecutablePath(path string) error {
 	}
 	GitExecutable = absPath
 
-	_, err = loadGitVersion()
-	if err != nil {
+	if err = loadGitVersion(); err != nil {
 		return fmt.Errorf("unable to load git version: %w", err)
 	}
 
@@ -105,6 +105,9 @@ func SetExecutablePath(path string) error {
 		return fmt.Errorf("installed git version %q is not supported, Gitea requires git version >= %q, %s", gitVersion.Original(), RequiredVersion, moreHint)
 	}
 
+	if err = checkGitVersionCompatibility(gitVersion); err != nil {
+		return fmt.Errorf("installed git version %s has a known compatibility issue with Gitea: %w, please upgrade (or downgrade) git", gitVersion.String(), err)
+	}
 	return nil
 }
 
@@ -262,19 +265,18 @@ func syncGitConfig() (err error) {
 		}
 	}
 
-	// Due to CVE-2022-24765, git now denies access to git directories which are not owned by current user
-	// however, some docker users and samba users find it difficult to configure their systems so that Gitea's git repositories are owned by the Gitea user. (Possibly Windows Service users - but ownership in this case should really be set correctly on the filesystem.)
-	// see issue: https://github.com/go-gitea/gitea/issues/19455
-	// Fundamentally the problem lies with the uid-gid-mapping mechanism for filesystems in docker on windows (and to a lesser extent samba).
-	// Docker's configuration mechanism for local filesystems provides no way of setting this mapping and although there is a mechanism for setting this uid through using cifs mounting it is complicated and essentially undocumented
-	// Thus the owner uid/gid for files on these filesystems will be marked as root.
+	// Due to CVE-2022-24765, git now denies access to git directories which are not owned by current user.
+	// However, some docker users and samba users find it difficult to configure their systems correctly,
+	// so that Gitea's git repositories are owned by the Gitea user.
+	// (Possibly Windows Service users - but ownership in this case should really be set correctly on the filesystem.)
+	// See issue: https://github.com/go-gitea/gitea/issues/19455
 	// As Gitea now always use its internal git config file, and access to the git repositories is managed through Gitea,
 	// it is now safe to set "safe.directory=*" for internal usage only.
-	// Please note: the wildcard "*" is only supported by Git 2.30.4/2.31.3/2.32.2/2.33.3/2.34.3/2.35.3/2.36 and later
-	// Although only supported by Git 2.30.4/2.31.3/2.32.2/2.33.3/2.34.3/2.35.3/2.36 and later - this setting is tolerated by earlier versions
+	// Although this setting is only supported by some new git versions, it is also tolerated by earlier versions
 	if err := configAddNonExist("safe.directory", "*"); err != nil {
 		return err
 	}
+
 	if runtime.GOOS == "windows" {
 		if err := configSet("core.longpaths", "true"); err != nil {
 			return err
@@ -307,8 +309,8 @@ func syncGitConfig() (err error) {
 
 // CheckGitVersionAtLeast check git version is at least the constraint version
 func CheckGitVersionAtLeast(atLeast string) error {
-	if _, err := loadGitVersion(); err != nil {
-		return err
+	if gitVersion == nil {
+		panic("git module is not initialized") // it shouldn't happen
 	}
 	atLeastVersion, err := version.NewVersion(atLeast)
 	if err != nil {
@@ -320,6 +322,21 @@ func CheckGitVersionAtLeast(atLeast string) error {
 	return nil
 }
 
+func checkGitVersionCompatibility(gitVer *version.Version) error {
+	badVersions := []struct {
+		Version *version.Version
+		Reason  string
+	}{
+		{version.Must(version.NewVersion("2.43.1")), "regression bug of GIT_FLUSH"},
+	}
+	for _, bad := range badVersions {
+		if gitVer.Equal(bad.Version) {
+			return errors.New(bad.Reason)
+		}
+	}
+	return nil
+}
+
 func configSet(key, value string) error {
 	stdout, _, err := NewCommand(DefaultContext, "config", "--global", "--get").AddDynamicArguments(key).RunStdString(nil)
 	if err != nil && !err.IsExitCode(1) {

modules/git/git_test.go

@@ -13,6 +13,7 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
 
+	"github.com/hashicorp/go-version"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -93,3 +94,25 @@ func TestSyncConfig(t *testing.T) {
 	assert.True(t, gitConfigContains("[sync-test]"))
 	assert.True(t, gitConfigContains("cfg-key-a = CfgValA"))
 }
+
+func TestParseGitVersion(t *testing.T) {
+	v, err := parseGitVersionLine("git version 2.29.3")
+	assert.NoError(t, err)
+	assert.Equal(t, "2.29.3", v.String())
+
+	v, err = parseGitVersionLine("git version 2.29.3.windows.1")
+	assert.NoError(t, err)
+	assert.Equal(t, "2.29.3", v.String())
+
+	_, err = parseGitVersionLine("git version")
+	assert.Error(t, err)
+
+	_, err = parseGitVersionLine("git version windows")
+	assert.Error(t, err)
+}
+
+func TestCheckGitVersionCompatibility(t *testing.T) {
+	assert.NoError(t, checkGitVersionCompatibility(version.Must(version.NewVersion("2.43.0"))))
+	assert.ErrorContains(t, checkGitVersionCompatibility(version.Must(version.NewVersion("2.43.1"))), "regression bug of GIT_FLUSH")
+	assert.NoError(t, checkGitVersionCompatibility(version.Must(version.NewVersion("2.43.2"))))
+}