feat(Settings): one can now set an AppSetting which is propogated down through child subcommands

Closes #519

Author: kbknapp

src/app/mod.rs

@@ -435,6 +435,53 @@ impl<'a, 'b> App<'a, 'b> {
         self
     }
 
+    /// Enables a single setting that is propogated *down* through all child [`SubCommand`]s.
+    ///
+    /// See [`AppSettings`] for a full list of possibilities and examples.
+    ///
+    /// **NOTE**: The setting is *only* propogated *down* and not up through parent commands.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # use clap::{App, Arg, AppSettings};
+    /// App::new("myprog")
+    ///     .global_setting(AppSettings::SubcommandRequired)
+    /// # ;
+    /// ```
+    /// [`SubCommand`]: ./struct.SubCommand.html
+    /// [`AppSettings`]: ./enum.AppSettings.html
+    pub fn global_setting(mut self, setting: AppSettings) -> Self {
+        self.p.set(setting);
+        self.p.g_settings.push(setting);
+        self
+    }
+
+    /// Enables multiple settings which are propogated *down* through all child [`SubCommand`]s.
+    ///
+    /// See [`AppSettings`] for a full list of possibilities and examples.
+    ///
+    /// **NOTE**: The setting is *only* propogated *down* and not up through parent commands.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # use clap::{App, Arg, AppSettings};
+    /// App::new("myprog")
+    ///     .global_settings(&[AppSettings::SubcommandRequired,
+    ///                  AppSettings::ColoredHelp])
+    /// # ;
+    /// ```
+    /// [`SubCommand`]: ./struct.SubCommand.html
+    /// [`AppSettings`]: ./enum.AppSettings.html
+    pub fn global_settings(mut self, settings: &[AppSettings]) -> Self {
+        for s in settings {
+            self.p.set(*s);
+            self.p.g_settings.push(*s)
+        }
+        self
+    }
+
     /// Adds an [argument] to the list of valid possibilties.
     ///
     /// # Examples

src/app/parser.rs

@@ -49,6 +49,7 @@ pub struct Parser<'a, 'b>
     help_short: Option<char>,
     version_short: Option<char>,
     settings: AppFlags,
+    pub g_settings: Vec<AppSettings>,
     pub meta: AppMeta<'b>,
 }
 
@@ -68,6 +69,7 @@ impl<'a, 'b> Default for Parser<'a, 'b> {
             groups: HashMap::new(),
             global_args: vec![],
             overrides: vec![],
+            g_settings: vec![],
             settings: AppFlags::new(),
             meta: AppMeta::new(),
         }
@@ -217,6 +219,10 @@ impl<'a, 'b> Parser<'a, 'b>
         if self.settings.is_set(AppSettings::DeriveDisplayOrder) {
             subcmd.p.meta.disp_ord = self.subcommands.len();
         }
+        for s in &self.g_settings {
+            subcmd.p.set(*s);
+            subcmd.p.g_settings.push(*s);
+        }
         self.subcommands.push(subcmd);
     }
 
@@ -1661,6 +1667,7 @@ impl<'a, 'b> Clone for Parser<'a, 'b>
             help_short: self.help_short,
             version_short: self.version_short,
             settings: self.settings.clone(),
+            g_settings: self.g_settings.clone(),
             meta: self.meta.clone(),
         }
     }