add(option): default_layout (#1467)

* add(option): `default_layout`

Add `option` `default_layout` / `default-layout`,
that allows specifying a different layout, that should
be loaded on start.

Eg:
```
default_layout: compact
```

* add(manpage): `default_layout`

docs/MANPAGE.md

@@ -39,6 +39,8 @@ LAYOUTS
 
 Layouts are yaml files which Zellij can load on startup when _--layout_ flag is
 provided.
+By default Zellij will load a layout called `default.yaml`,
+but this can be changed by using the `default_layout: [LAYOUT_NAME]` configuration option.
 
 
 For example a file like this:

zellij-utils/src/input/options.rs

@@ -52,6 +52,9 @@ pub struct Options {
     /// Set the default shell
     #[clap(long, parse(from_os_str))]
     pub default_shell: Option<PathBuf>,
+    /// Set the default layout
+    #[clap(long, parse(from_os_str))]
+    pub default_layout: Option<PathBuf>,
     /// Set the layout_dir, defaults to
     /// subdirectory of config dir
     #[clap(long, parse(from_os_str))]
@@ -128,6 +131,7 @@ impl Options {
         let simplified_ui = other.simplified_ui.or(self.simplified_ui);
         let default_mode = other.default_mode.or(self.default_mode);
         let default_shell = other.default_shell.or_else(|| self.default_shell.clone());
+        let default_layout = other.default_layout.or_else(|| self.default_layout.clone());
         let layout_dir = other.layout_dir.or_else(|| self.layout_dir.clone());
         let theme = other.theme.or_else(|| self.theme.clone());
         let on_force_close = other.on_force_close.or(self.on_force_close);
@@ -144,6 +148,7 @@ impl Options {
             theme,
             default_mode,
             default_shell,
+            default_layout,
             layout_dir,
             mouse_mode,
             pane_frames,
@@ -179,6 +184,7 @@ impl Options {
 
         let default_mode = other.default_mode.or(self.default_mode);
         let default_shell = other.default_shell.or_else(|| self.default_shell.clone());
+        let default_layout = other.default_layout.or_else(|| self.default_layout.clone());
         let layout_dir = other.layout_dir.or_else(|| self.layout_dir.clone());
         let theme = other.theme.or_else(|| self.theme.clone());
         let on_force_close = other.on_force_close.or(self.on_force_close);
@@ -195,6 +201,7 @@ impl Options {
             theme,
             default_mode,
             default_shell,
+            default_layout,
             layout_dir,
             mouse_mode,
             pane_frames,
@@ -247,6 +254,7 @@ impl From<CliOptions> for Options {
             theme: opts.theme,
             default_mode: opts.default_mode,
             default_shell: opts.default_shell,
+            default_layout: opts.default_layout,
             layout_dir: opts.layout_dir,
             mouse_mode: opts.mouse_mode,
             pane_frames: opts.pane_frames,

zellij-utils/src/setup.rs

@@ -230,8 +230,12 @@ impl Setup {
             .layout_dir
             .clone()
             .or_else(|| get_layout_dir(opts.config_dir.clone().or_else(find_default_config_dir)));
+        let chosen_layout = opts
+            .layout
+            .clone()
+            .or_else(|| config_options.default_layout.clone());
         let layout_result =
-            LayoutFromYamlIntermediate::from_path_or_default(opts.layout.as_ref(), layout_dir);
+            LayoutFromYamlIntermediate::from_path_or_default(chosen_layout.as_ref(), layout_dir);
         let layout = match layout_result {
             None => None,
             Some(Ok(layout)) => Some(layout),