Refactor for better modularity (share more code among edit functions, rename "offline" package to "backend"

src/backend/initUNIX.go

@@ -0,0 +1,37 @@
+//go:build !windows
+
+package backend
+
+import (
+	"fmt"
+	"os"
+)
+
+const FallbackEditor = "vi" // vi is pre-installed on most UNIX systems
+
+// dirInit creates the libmutton directories
+func dirInit() {
+	// create EntryRoot
+	err := os.MkdirAll(EntryRoot, 0700)
+	if err != nil {
+		fmt.Println(AnsiError + "Failed to create \"" + EntryRoot + "\":" + err.Error() + AnsiReset)
+		os.Exit(1)
+	}
+
+	// create config directory
+	err = os.MkdirAll(ConfigDir, 0700)
+	if err != nil {
+		fmt.Println(AnsiError + "Failed to create \"" + ConfigDir + "\":" + err.Error() + AnsiReset)
+		os.Exit(1)
+	}
+}
+
+// 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
+}