gitutil: add opt-in support for host git config

util/gitutil/git_cli.go

@@ -27,6 +27,7 @@ type GitCLI struct {
 
 	sshAuthSock   string
 	sshKnownHosts string
+	hostGitConfig bool
 }
 
 // Option provides a variadic option for configuring the git client.
@@ -97,6 +98,15 @@ func WithSSHKnownHosts(sshKnownHosts string) Option {
 	}
 }
 
+// WithHostGitConfig allows git to read the host system and user git config.
+// This is intended for client-side local git inspection. The default remains
+// isolated so daemon-side callers do not leak host configuration into git.
+func WithHostGitConfig() Option {
+	return func(b *GitCLI) {
+		b.hostGitConfig = true
+	}
+}
+
 type StreamFunc func(context.Context) (io.WriteCloser, io.WriteCloser, func())
 
 // WithStreams configures a callback for getting the streams for a command. The
@@ -108,7 +118,7 @@ func WithStreams(streams StreamFunc) Option {
 	}
 }
 
-// New initializes a new git client
+// NewGitCLI New initializes a new git client
 func NewGitCLI(opts ...Option) *GitCLI {
 	c := &GitCLI{}
 	for _, opt := range opts {
@@ -191,9 +201,27 @@ func (cli *GitCLI) Run(ctx context.Context, args ...string) (_ []byte, err error
 			"GIT_TERMINAL_PROMPT=0",
 			"GIT_SSH_COMMAND=" + getGitSSHCommand(cli.sshKnownHosts),
 			//	"GIT_TRACE=1",
-			"GIT_CONFIG_NOSYSTEM=1", // Disable reading from system gitconfig.
-			"HOME=/dev/null",        // Disable reading from user gitconfig.
-			"LC_ALL=C",              // Ensure consistent output.
+			"LC_ALL=C", // Ensure consistent output.
+		}
+		if cli.hostGitConfig {
+			for _, ev := range [...]string{
+				"HOME",
+				"XDG_CONFIG_HOME",
+				"USERPROFILE",
+				"HOMEDRIVE",
+				"HOMEPATH",
+				"GIT_CONFIG_GLOBAL",
+				"GIT_CONFIG_SYSTEM",
+			} {
+				if v, ok := os.LookupEnv(ev); ok {
+					cmd.Env = append(cmd.Env, ev+"="+v)
+				}
+			}
+		} else {
+			cmd.Env = append(cmd.Env,
+				"GIT_CONFIG_NOSYSTEM=1", // Disable reading from system gitconfig.
+				"HOME=/dev/null",        // Disable reading from user gitconfig.
+			)
 		}
 		for _, ev := range proxyEnvVars {
 			if v, ok := os.LookupEnv(ev); ok {

util/gitutil/git_cli_test.go

@@ -0,0 +1,57 @@
+package gitutil
+
+import (
+	"context"
+	"os/exec"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestGitCLIConfigEnv(t *testing.T) {
+	t.Setenv("HOME", "/tmp/home")
+	t.Setenv("XDG_CONFIG_HOME", "/tmp/xdg")
+	t.Setenv("USERPROFILE", `C:\Users\tester`)
+	t.Setenv("HOMEDRIVE", "C:")
+	t.Setenv("HOMEPATH", `\Users\tester`)
+	t.Setenv("GIT_CONFIG_GLOBAL", "/tmp/global-gitconfig")
+	t.Setenv("GIT_CONFIG_SYSTEM", "/tmp/system-gitconfig")
+
+	t.Run("isolated by default", func(t *testing.T) {
+		var got []string
+		cli := NewGitCLI(WithExec(func(ctx context.Context, cmd *exec.Cmd) error {
+			got = append([]string(nil), cmd.Env...)
+			return nil
+		}))
+		_, err := cli.Run(context.Background(), "status")
+		require.NoError(t, err)
+		require.Contains(t, got, "GIT_CONFIG_NOSYSTEM=1")
+		require.Contains(t, got, "HOME=/dev/null")
+		require.NotContains(t, got, "HOME=/tmp/home")
+		require.NotContains(t, got, "XDG_CONFIG_HOME=/tmp/xdg")
+		require.NotContains(t, got, "GIT_CONFIG_GLOBAL=/tmp/global-gitconfig")
+		require.NotContains(t, got, "GIT_CONFIG_SYSTEM=/tmp/system-gitconfig")
+	})
+
+	t.Run("host git config opt-in", func(t *testing.T) {
+		var got []string
+		cli := NewGitCLI(
+			WithHostGitConfig(),
+			WithExec(func(ctx context.Context, cmd *exec.Cmd) error {
+				got = append([]string(nil), cmd.Env...)
+				return nil
+			}),
+		)
+		_, err := cli.Run(context.Background(), "status")
+		require.NoError(t, err)
+		require.NotContains(t, got, "GIT_CONFIG_NOSYSTEM=1")
+		require.NotContains(t, got, "HOME=/dev/null")
+		require.Contains(t, got, "HOME=/tmp/home")
+		require.Contains(t, got, "XDG_CONFIG_HOME=/tmp/xdg")
+		require.Contains(t, got, `USERPROFILE=C:\Users\tester`)
+		require.Contains(t, got, "HOMEDRIVE=C:")
+		require.Contains(t, got, `HOMEPATH=\Users\tester`)
+		require.Contains(t, got, "GIT_CONFIG_GLOBAL=/tmp/global-gitconfig")
+		require.Contains(t, got, "GIT_CONFIG_SYSTEM=/tmp/system-gitconfig")
+	})
+}