ls-fonts: refine output a bit

It now outputs something that you could conceivably put into
your config file, although the intent is to show the canonical
way to reference the individual fonts that were found, rather
than to specify a fully baked list to paste into a config.

eg:

```
; ./target/debug/wezterm ls-fonts
Primary font:
wezterm.font_with_fallback({
  -- /home/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontDirs
  {family="Operator Mono SSm Lig", weight="DemiLight"},

  -- /home/wez/.fonts/OperatorMonoSSmLig-Medium.otf, FontConfig
  {family="Operator Mono SSm Lig", weight="DemiLight"},

  -- /home/wez/.fonts/MaterialDesignIconsDesktop.ttf, FontDirs
  "Material Design Icons Desktop",

  -- /home/wez/.fonts/terminus-bold.otb, FontDirs
  {family="Terminus", weight="Bold"},

  -- /home/wez/.fonts/JetBrainsMono-Regular.ttf, FontDirs
  "JetBrains Mono",

  -- /home/wez/.fonts/NotoColorEmoji.ttf, FontDirs
  "Noto Color Emoji",

  -- /home/wez/.fonts/MaterialDesignIconsDesktop.ttf, FontConfig
  "Material Design Icons Desktop",

  -- /usr/share/fonts/terminus-fonts/ter-u32n.otb, FontConfig
  "Terminus",

  -- /home/wez/.fonts/JetBrainsMono-Regular.ttf, FontConfig
  "JetBrains Mono",

  -- /home/wez/.fonts/NotoColorEmoji.ttf, FontConfig
  "Noto Color Emoji",

  -- <built-in>, BuiltIn
  "Last Resort High-Efficiency",

})
```

wezterm-font/src/parser.rs

@@ -125,6 +125,33 @@ impl ParsedFont {
         )
     }
 
+    pub fn lua_fallback(handles: &[Self]) -> String {
+        let mut code = "wezterm.font_with_fallback({\n".to_string();
+
+        for p in handles {
+            code.push_str(&format!("  -- {}\n", p.handle.diagnostic_string()));
+
+            if p.weight == FontWeight::Regular && p.stretch == FontStretch::Normal && !p.italic {
+                code.push_str(&format!("  \"{}\",\n", p.names.family));
+            } else {
+                code.push_str(&format!("  {{family=\"{}\"", p.names.family));
+                if p.weight != FontWeight::Regular {
+                    code.push_str(&format!(", weight=\"{}\"", p.weight));
+                }
+                if p.stretch != FontStretch::Normal {
+                    code.push_str(&format!(", stretch=\"{}\"", p.stretch));
+                }
+                if p.italic {
+                    code.push_str(", italic=true");
+                }
+                code.push_str("},\n")
+            }
+            code.push_str("\n");
+        }
+        code.push_str("})");
+        code
+    }
+
     pub fn from_face(face: &crate::ftwrap::Face, handle: FontDataHandle) -> anyhow::Result<Self> {
         let italic = face.italic();
         let (weight, width) = face.weight_and_width();

wezterm-gui/src/main.rs

@@ -414,6 +414,8 @@ fn maybe_show_configuration_error_window() {
 }
 
 pub fn run_ls_fonts(config: config::ConfigHandle, _cmd: &LsFontsCommand) -> anyhow::Result<()> {
+    use wezterm_font::parser::ParsedFont;
+
     // Disable the normal config error UI window, as we don't have
     // a fully baked GUI environment running
     config::assign_error_callback(|err| eprintln!("{}", err));
@@ -422,11 +424,11 @@ pub fn run_ls_fonts(config: config::ConfigHandle, _cmd: &LsFontsCommand) -> anyh
 
     println!("Primary font:");
     let default_font = font_config.default_font()?;
-    for f in default_font.clone_handles() {
+    println!(
-        println!("  {}", f.lua_name());
+        "{}",
-        println!("    ({})", f.handle.diagnostic_string());
+        ParsedFont::lua_fallback(&default_font.clone_handles())
+    );
     println!();
-    }
 
     for rule in &config.font_rules {
         println!();
@@ -456,12 +458,9 @@ pub fn run_ls_fonts(config: config::ConfigHandle, _cmd: &LsFontsCommand) -> anyh
 
         println!("{}:", condition);
         let font = font_config.resolve_font(&rule.font)?;
-        for f in font.clone_handles() {
+        println!("{}", ParsedFont::lua_fallback(&font.clone_handles()));
-            println!("  {}", f.lua_name());
-            println!("    ({})", f.handle.diagnostic_string());
         println!();
     }
-    }
 
     Ok(())
 }