[codex] Hide git runner console windows on Windows

git/cmd/gitcmd.go

@@ -93,7 +93,7 @@ func (r Runner) Command(ctx context.Context, dir string, args ...string) *exec.C
 	if r.basicAuth != nil {
 		panic("gitcmd: Command cannot be used with WithBasicAuth; use Run or Output so credentials can be cleaned up")
 	}
-	cmd := exec.CommandContext(ctx, "git", args...)
+	cmd := gitCommand(ctx, args...)
 	cmd.Dir = dir
 	cmd.Env, _ = r.commandEnv(ctx, dir)
 	return cmd
@@ -107,7 +107,7 @@ func (r Runner) Output(ctx context.Context, dir string, args ...string) ([]byte,
 
 // Run runs git and returns stdout, stderr, and a *GitError on failure.
 func (r Runner) Run(ctx context.Context, dir string, stdin io.Reader, args ...string) ([]byte, []byte, error) {
-	cmd := exec.CommandContext(ctx, "git", args...)
+	cmd := gitCommand(ctx, args...)
 	cmd.Dir = dir
 	var cleanup func()
 	cmd.Env, cleanup = r.commandEnv(ctx, dir)
@@ -131,6 +131,12 @@ func (r Runner) Run(ctx context.Context, dir string, stdin io.Reader, args ...st
 	return stdout.Bytes(), stderr.Bytes(), nil
 }
 
+func gitCommand(ctx context.Context, args ...string) *exec.Cmd {
+	cmd := exec.CommandContext(ctx, "git", args...)
+	prepareGitCommand(cmd)
+	return cmd
+}
+
 type basicAuth struct {
 	username string
 	password string
@@ -231,7 +237,7 @@ func readSafeDirectories(ctx context.Context, env []string, dir string) []string
 	for _, scope := range scopes {
 		// --includes is required for explicit-scope reads to honor include.path
 		// and includeIf directives the way git's default config sequence does.
-		cmd := exec.CommandContext(ctx, "git", "config", scope, "--includes", "-z", "--get-all", "safe.directory")
+		cmd := gitCommand(ctx, "config", scope, "--includes", "-z", "--get-all", "safe.directory")
 		cmd.Dir = dir
 		cmd.Env = env
 		out, err := cmd.Output()

git/cmd/gitcmd_other.go

@@ -0,0 +1,7 @@
+//go:build !windows
+
+package gitcmd
+
+import "os/exec"
+
+func prepareGitCommand(cmd *exec.Cmd) {}

git/cmd/gitcmd_windows.go

@@ -0,0 +1,18 @@
+//go:build windows
+
+package gitcmd
+
+import (
+	"os/exec"
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+func prepareGitCommand(cmd *exec.Cmd) {
+	if cmd.SysProcAttr == nil {
+		cmd.SysProcAttr = &syscall.SysProcAttr{}
+	}
+	// Console-less callers otherwise cause git.exe to allocate a visible window.
+	cmd.SysProcAttr.CreationFlags |= windows.CREATE_NO_WINDOW
+}

git/cmd/gitcmd_windows_test.go

@@ -0,0 +1,21 @@
+//go:build windows
+
+package gitcmd
+
+import (
+	"context"
+	"testing"
+
+	"golang.org/x/sys/windows"
+)
+
+func TestRunnerCommandHidesGitConsoleWindowOnWindows(t *testing.T) {
+	cmd := New().Command(context.Background(), "", "status")
+
+	if cmd.SysProcAttr == nil {
+		t.Fatal("git command SysProcAttr is nil")
+	}
+	if cmd.SysProcAttr.CreationFlags&windows.CREATE_NO_WINDOW == 0 {
+		t.Fatalf("git command creation flags = %#x, want CREATE_NO_WINDOW", cmd.SysProcAttr.CreationFlags)
+	}
+}