feat(Global Args): allows args that propagate down to child commands

Closes #131

src/app.rs

@@ -118,6 +118,7 @@ pub struct App<'a, 'v, 'ab, 'u, 'h, 'ar> {
     bin_name: Option<String>,
     usage: Option<String>,
     groups: HashMap<&'ar str, ArgGroup<'ar, 'ar>>,
+    global_args: Vec<Arg<'ar, 'ar, 'ar, 'ar, 'ar, 'ar>>,
     no_sc_error: bool
 }
 
@@ -161,6 +162,7 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
             bin_name: None,
             groups: HashMap::new(),
             subcmds_neg_reqs: false,
+            global_args: vec![],
             no_sc_error: false
         }
     }
@@ -419,6 +421,7 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
                 min_vals: a.min_vals,
                 max_vals: a.max_vals,
                 help: a.help,
+                global: a.global,
                 empty_vals: a.empty_vals
             };
             if pb.min_vals.is_some() && !pb.multiple {
@@ -470,11 +473,12 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
                 multiple: a.multiple,
                 blacklist: None,
                 help: a.help,
+                global: a.global,
                 possible_vals: None,
                 num_vals: a.num_vals,
                 min_vals: a.min_vals,
                 max_vals: a.max_vals,
-                val_names: a.val_names,
+                val_names: a.val_names.clone(),
                 requires: None,
                 required: a.required,
                 empty_vals: a.empty_vals
@@ -540,6 +544,7 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
                 long: a.long,
                 help: a.help,
                 blacklist: None,
+                global: a.global,
                 multiple: a.multiple,
                 requires: None,
             };
@@ -560,6 +565,12 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
             }
             self.flags.insert(a.name, fb);
         }
+        if a.global {
+            if a.required {
+                panic!("Global arguments cannot be required.\n\n\t'{}' is marked as global and required", a.name);
+            }
+            self.global_args.push(a);
+        }
         self
     }
 
@@ -749,9 +760,14 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
     ///             // Additional subcommand configuration goes here, such as other arguments...
     /// # .get_matches();
     /// ```
-    pub fn subcommand(mut self, subcmd: App<'a, 'v, 'ab, 'u, 'h, 'ar>)
+    pub fn subcommand(mut self, mut subcmd: App<'a, 'v, 'ab, 'u, 'h, 'ar>)
                       -> App<'a, 'v, 'ab, 'u, 'h, 'ar> {
         if subcmd.name == "help" { self.needs_subcmd_help = false; }
+        {
+            while let Some(a) = self.global_args.pop() {
+                subcmd = subcmd.arg(a);
+            }
+        }
         self.subcommands.insert(subcmd.name.clone(), subcmd);
         self
     }
@@ -1763,6 +1779,7 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
                 help: Some("Prints help information"),
                 blacklist: None,
                 multiple: false,
+                global: false,
                 requires: None,
             };
             if self.needs_short_help {
@@ -1780,6 +1797,7 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
                 help: Some("Prints version information"),
                 blacklist: None,
                 multiple: false,
+                global: false,
                 requires: None,
             };
             if self.needs_short_version {

src/args/arg.rs

@@ -133,6 +133,7 @@ impl<'n, 'l, 'h, 'g, 'p, 'r> Arg<'n, 'l, 'h, 'g, 'p, 'r> {
             val_names: None,
             max_vals: None,
             min_vals: None,
+            global: false,
             empty_vals: true,
         }
     }
@@ -173,6 +174,7 @@ impl<'n, 'l, 'h, 'g, 'p, 'r> Arg<'n, 'l, 'h, 'g, 'p, 'r> {
             max_vals: None,
             val_names: None,
             group: None,
+            global: false,
             empty_vals: true
         }
     }
@@ -330,6 +332,7 @@ impl<'n, 'l, 'h, 'g, 'p, 'r> Arg<'n, 'l, 'h, 'g, 'p, 'r> {
             max_vals: None,
             min_vals: None,
             group: None,
+            global: false,
             empty_vals: true
         }
     }
@@ -646,8 +649,9 @@ impl<'n, 'l, 'h, 'g, 'p, 'r> Arg<'n, 'l, 'h, 'g, 'p, 'r> {
         self
     }
 
-    /// Specifies that an argument applies to and will be available to all subcommands, both
+    /// Specifies that an argument applies to and will be available to all child subcommands.
-    /// children, and parent commands.
+    ///
+    /// **NOTE:** Global arguments *only* propagate down, **not** up (to parent commands)
     ///
     /// **NOTE:** Global arguments *cannot* be required.
     ///

src/args/argbuilder/flag.rs

@@ -24,6 +24,7 @@ pub struct FlagBuilder<'n> {
     /// The short version (i.e. single character)
     /// of the argument, no preceding `-`
     pub short: Option<char>,
+    pub global: bool,
 }
 
 impl<'n> Display for FlagBuilder<'n> {

src/args/argbuilder/option.rs

@@ -29,7 +29,8 @@ pub struct OptBuilder<'n> {
     pub min_vals: Option<u8>,
     pub max_vals: Option<u8>,
     pub val_names: Option<Vec<&'n str>>,
-    pub empty_vals: bool
+    pub empty_vals: bool,
+    pub global: bool,
 }
 
 impl<'n> Display for OptBuilder<'n> {

src/args/argbuilder/positional.rs

@@ -26,7 +26,8 @@ pub struct PosBuilder<'n> {
     pub num_vals: Option<u8>,
     pub max_vals: Option<u8>,
     pub min_vals: Option<u8>,
-    pub empty_vals: bool
+    pub empty_vals: bool,
+    pub global: bool
 }
 
 impl<'n> Display for PosBuilder<'n> {