dev: fix slice bounds panic

Squash a bug I introduced in #76189; we were assuming a minimum slice
length when we shouldn't have.

Release note: None

dev

@@ -3,7 +3,7 @@
 set -euo pipefail
 
 # Bump this counter to force rebuilding `dev` on all machines.
-DEV_VERSION=13
+DEV_VERSION=14
 
 THIS_DIR=$(cd "$(dirname "$0")" && pwd)
 BINARY_DIR=$THIS_DIR/bin/dev-versions

pkg/cmd/dev/io/os/os.go

@@ -213,7 +213,14 @@ func (o *OS) ReadFile(filename string) (string, error) {
 // WriteFile wraps around ioutil.ReadFile, writing the given contents to
 // the given file on disk.
 func (o *OS) WriteFile(filename, contents string) error {
-	command := fmt.Sprintf("echo %q > %s", strings.TrimSpace(contents[:10]), filename)
+	var command string
+	{
+		commandContents := contents
+		if len(commandContents) > 10 {
+			commandContents = commandContents[:10] // keeps the logging manageable
+		}
+		command = fmt.Sprintf("echo %q > %s", strings.TrimSpace(commandContents), filename)
+	}
 	o.logger.Print(command)
 
 	_, err := o.Next(command, func() (output string, err error) {