Move text editor determination to cli package

src/cli/initUNIX.go

@@ -0,0 +1,19 @@
+//go:build !windows
+
+package cli
+
+import (
+	"os"
+)
+
+const fallbackEditor = "vi" // vi is pre-installed on most UNIX systems
+
+// textEditorFallback returns the value of the $EDITOR environment variable, or FallbackEditor if it is not set
+func textEditorFallback() string {
+	// ensure textEditor is set
+	textEditor := os.Getenv("EDITOR")
+	if textEditor == "" {
+		textEditor = fallbackEditor
+	}
+	return textEditor
+}