edit: Make it more user-friendly

apps/edit.cpp

@@ -1,6 +1,8 @@
 #include <luna/String.h>
 #include <os/ArgumentParser.h>
 #include <os/File.h>
+#include <os/FileSystem.h>
+#include <os/Prompt.h>
 
 using os::File;
 
@@ -14,10 +16,20 @@ Result<int> luna_main(int argc, char** argv)
     parser.add_positional_argument(pathname, "path"_sv, true);
     parser.parse(argc, argv);
 
+    if (os::FileSystem::exists(pathname))
+    {
+        String prompt = TRY(String::format("File %s already exists. Overwrite?"_sv, pathname.chars()));
+        bool overwrite = os::conditional_prompt(prompt.chars(), os::DefaultNo);
+        if (!overwrite) return 0;
+    }
+
     auto file = TRY(File::open_or_create(pathname, File::WriteOnly));
 
     auto input = File::standard_input();
 
+    os::println("- Editing %s. Press Enter to start a new line, or Ctrl+D at the start of a line to save and exit. -",
+                pathname.chars());
+
     while (1)
     {
         String line = TRY(input->read_line());