diff --git a/README.md b/README.md
index c5109dcb9f7..09e8f0c27e7 100644
--- a/README.md
+++ b/README.md
@@ -444,7 +444,7 @@ Disabling optional features can decrease the binary size of `clap` and decrease
 * **std**: _Not Currently Used._ Placeholder for supporting `no_std` environments in a backwards compatible manner.
 * **derive**: Enables the custom derive (i.e. `#[derive(Parser)]`). Without this you must use one of the other methods of creating a `clap` CLI listed above. (builds dependency `clap_derive`)
 * **cargo**: Turns on macros that read values from `CARGO_*` environment variables.
-* **color**: Turns on colored error messages. (builds dependency `termcolor`)
+* **color**: Turns on colored error messages. (builds dependency `atty`, `termcolor`)
 * **env**: Turns on the usage of environment variables during parsing.
 * **suggestions**: Turns on the `Did you mean '--myoption'?` feature for when users make typos. (builds dependency `strsim`)
 * **unicode**: Turns on support for unicode characters in arguments and help messages. (builds dependency `textwrap`, `unicase`)
diff --git a/clap_derive/src/lib.rs b/clap_derive/src/lib.rs
index 23fa383ae60..110c87a5b80 100644
--- a/clap_derive/src/lib.rs
+++ b/clap_derive/src/lib.rs
@@ -16,7 +16,7 @@
 #![doc(html_root_url = "https://docs.rs/clap_derive/3.0.0-beta.4")]
 
 //! This crate is custom derive for clap. It should not be used
-//! directly. See [clap documentation](clap)
+//! directly. See [clap documentation](http://docs.rs/clap)
 //! for the usage of `#[derive(Parser)]`.
 
 #![forbid(unsafe_code)]
diff --git a/src/build/app/mod.rs b/src/build/app/mod.rs
index 6ba45b095f8..51d0713ec42 100644
--- a/src/build/app/mod.rs
+++ b/src/build/app/mod.rs
@@ -28,7 +28,7 @@ use crate::{
     mkeymap::MKeyMap,
     output::{fmt::Colorizer, Help, HelpWriter, Usage},
     parse::{ArgMatcher, ArgMatches, Input, Parser},
-    util::{safe_exit, termcolor::ColorChoice, Id, Key, USAGE_CODE},
+    util::{color::ColorChoice, safe_exit, Id, Key, USAGE_CODE},
     Result as ClapResult, INTERNAL_ERROR_MSG,
 };
 
@@ -90,6 +90,7 @@ pub struct App<'help> {
     pub(crate) template: Option<&'help str>,
     pub(crate) settings: AppFlags,
     pub(crate) g_settings: AppFlags,
+    pub(crate) color: ColorChoice,
     pub(crate) args: MKeyMap<'help>,
     pub(crate) subcommands: Vec<App<'help>>,
     pub(crate) replacers: HashMap<&'help str, &'help [&'help str]>,
@@ -985,7 +986,7 @@ impl<'help> App<'help> {
     /// ```no_run
     /// # use clap::{App, AppSettings};
     /// App::new("myprog")
-    ///     .unset_global_setting(AppSettings::ColorAuto)
+    ///     .unset_global_setting(AppSettings::UnifiedHelpMessage)
     /// # ;
     /// ```
     /// [global]: App::global_setting()
@@ -996,6 +997,28 @@ impl<'help> App<'help> {
         self
     }
 
+    /// Sets the behaviour of colored output during runtime.
+    ///
+    /// **NOTE:** This choice is propagated to all child subcommands.
+    ///
+    /// **NOTE:** Default behaviour is [`ColorChoice::Auto`].
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # use clap::{App, ColorChoice};
+    /// App::new("myprog")
+    ///     .color(ColorChoice::Never)
+    ///     .get_matches();
+    /// ```
+    /// [`ColorChoice::Auto`]: crate::ColorChoice::Auto
+    #[cfg(feature = "color")]
+    #[inline]
+    pub fn color(mut self, color: ColorChoice) -> Self {
+        self.color = color;
+        self
+    }
+
     /// Sets the terminal width at which to wrap help messages. Defaults to
     /// `100`. Using `0` will ignore terminal widths and use source formatting.
     ///
@@ -1788,7 +1811,7 @@ impl<'help> App<'help> {
     /// [`--help` (long)]: Arg::long_about()
     pub fn print_help(&mut self) -> io::Result<()> {
         self._build();
-        let color = self.color();
+        let color = self.get_color();
 
         let p = Parser::new(self);
         let mut c = Colorizer::new(false, color);
@@ -1815,7 +1838,7 @@ impl<'help> App<'help> {
     /// [`--help` (long)]: Arg::long_about()
     pub fn print_long_help(&mut self) -> io::Result<()> {
         self._build();
-        let color = self.color();
+        let color = self.get_color();
 
         let p = Parser::new(self);
         let mut c = Colorizer::new(false, color);
@@ -2656,20 +2679,8 @@ impl<'help> App<'help> {
     }
 
     #[inline]
-    // Should we color the output?
-    pub(crate) fn color(&self) -> ColorChoice {
-        debug!("App::color: Color setting...");
-
-        if self.is_set(AppSettings::ColorNever) {
-            debug!("Never");
-            ColorChoice::Never
-        } else if self.is_set(AppSettings::ColorAlways) {
-            debug!("Always");
-            ColorChoice::Always
-        } else {
-            debug!("Auto");
-            ColorChoice::Auto
-        }
+    pub(crate) fn get_color(&self) -> ColorChoice {
+        self.color
     }
 
     #[inline]
diff --git a/src/build/app/settings.rs b/src/build/app/settings.rs
index c462626d708..aebd9b6b5e6 100644
--- a/src/build/app/settings.rs
+++ b/src/build/app/settings.rs
@@ -26,10 +26,6 @@ bitflags! {
         const NO_POS_VALUES                  = 1 << 17;
         const NEXT_LINE_HELP                 = 1 << 18;
         const DERIVE_DISP_ORDER              = 1 << 19;
-        const COLORED_HELP                   = 1 << 20;
-        const COLOR_ALWAYS                   = 1 << 21;
-        const COLOR_AUTO                     = 1 << 22;
-        const COLOR_NEVER                    = 1 << 23;
         const DONT_DELIM_TRAIL               = 1 << 24;
         const ALLOW_NEG_NUMS                 = 1 << 25;
         const DISABLE_HELP_SC                = 1 << 27;
@@ -59,7 +55,7 @@ pub struct AppFlags(Flags);
 
 impl Default for AppFlags {
     fn default() -> Self {
-        AppFlags(Flags::COLOR_AUTO)
+        Self::empty()
     }
 }
 
@@ -80,12 +76,6 @@ impl_settings! { AppSettings, AppFlags,
         => Flags::ALLOW_NEG_NUMS,
     AllowMissingPositional("allowmissingpositional")
         => Flags::ALLOW_MISSING_POS,
-    ColorAlways("coloralways")
-        => Flags::COLOR_ALWAYS,
-    ColorAuto("colorauto")
-        => Flags::COLOR_AUTO,
-    ColorNever("colornever")
-        => Flags::COLOR_NEVER,
     DontDelimitTrailingValues("dontdelimittrailingvalues")
         => Flags::DONT_DELIM_TRAIL,
     DontCollapseArgsInUsage("dontcollapseargsinusage")
@@ -491,62 +481,6 @@ pub enum AppSettings {
     /// ```
     SubcommandPrecedenceOverArg,
 
-    /// Enables colored output only when the output is going to a terminal or TTY.
-    ///
-    /// **NOTE:** This is the default behavior of `clap`.
-    ///
-    /// **NOTE:** Must be compiled with the `color` cargo feature.
-    ///
-    /// # Platform Specific
-    ///
-    /// This setting only applies to Unix, Linux, and OSX (i.e. non-Windows platforms).
-    ///
-    /// # Examples
-    ///
-    /// ```no_run
-    /// # use clap::{App, Arg, AppSettings};
-    /// App::new("myprog")
-    ///     .setting(AppSettings::ColorAuto)
-    ///     .get_matches();
-    /// ```
-    ColorAuto,
-
-    /// Enables colored output regardless of whether or not the output is going to a terminal/TTY.
-    ///
-    /// **NOTE:** Must be compiled with the `color` cargo feature.
-    ///
-    /// # Platform Specific
-    ///
-    /// This setting only applies to Unix, Linux, and OSX (i.e. non-Windows platforms).
-    ///
-    /// # Examples
-    ///
-    /// ```no_run
-    /// # use clap::{App, Arg, AppSettings};
-    /// App::new("myprog")
-    ///     .setting(AppSettings::ColorAlways)
-    ///     .get_matches();
-    /// ```
-    ColorAlways,
-
-    /// Disables colored output no matter if the output is going to a terminal/TTY, or not.
-    ///
-    /// **NOTE:** Must be compiled with the `color` cargo feature
-    ///
-    /// # Platform Specific
-    ///
-    /// This setting only applies to Unix, Linux, and OSX (i.e. non-Windows platforms)
-    ///
-    /// # Examples
-    ///
-    /// ```no_run
-    /// # use clap::{App, Arg, AppSettings};
-    /// App::new("myprog")
-    ///     .setting(AppSettings::ColorNever)
-    ///     .get_matches();
-    /// ```
-    ColorNever,
-
     /// Disables the automatic collapsing of positional args into `[ARGS]` inside the usage string
     ///
     /// # Examples
@@ -1086,18 +1020,6 @@ mod test {
             "allownegativenumbers".parse::<AppSettings>().unwrap(),
             AppSettings::AllowNegativeNumbers
         );
-        assert_eq!(
-            "colorauto".parse::<AppSettings>().unwrap(),
-            AppSettings::ColorAuto
-        );
-        assert_eq!(
-            "coloralways".parse::<AppSettings>().unwrap(),
-            AppSettings::ColorAlways
-        );
-        assert_eq!(
-            "colornever".parse::<AppSettings>().unwrap(),
-            AppSettings::ColorNever
-        );
         assert_eq!(
             "disablehelpsubcommand".parse::<AppSettings>().unwrap(),
             AppSettings::DisableHelpSubcommand
diff --git a/src/lib.rs b/src/lib.rs
index 0c44c350c90..24899e30c80 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -29,6 +29,7 @@ pub use crate::{
     },
     parse::errors::{Error, ErrorKind, Result},
     parse::{ArgMatches, Indices, OsValues, Values},
+    util::color::ColorChoice,
 };
 
 pub use crate::derive::{ArgEnum, Args, FromArgMatches, IntoApp, Parser, Subcommand};
diff --git a/src/output/fmt.rs b/src/output/fmt.rs
index 6c898b92026..267feb18053 100644
--- a/src/output/fmt.rs
+++ b/src/output/fmt.rs
@@ -1,7 +1,4 @@
-#[cfg(not(feature = "color"))]
-use crate::util::termcolor::{Color, ColorChoice};
-#[cfg(feature = "color")]
-use termcolor::{Color, ColorChoice};
+use crate::util::color::{Color, ColorChoice};
 
 use std::{
     fmt::{self, Display, Formatter},
@@ -63,12 +60,12 @@ impl Colorizer {
 impl Colorizer {
     #[cfg(feature = "color")]
     pub(crate) fn print(&self) -> io::Result<()> {
-        use termcolor::{BufferWriter, ColorSpec, WriteColor};
+        use termcolor::{BufferWriter, ColorChoice as DepColorChoice, ColorSpec, WriteColor};
 
         let color_when = match self.color_when {
-            always @ ColorChoice::Always => always,
-            choice if is_a_tty(self.use_stderr) => choice,
-            _ => ColorChoice::Never,
+            ColorChoice::Always => DepColorChoice::Always,
+            ColorChoice::Auto if is_a_tty(self.use_stderr) => DepColorChoice::Auto,
+            _ => DepColorChoice::Never,
         };
 
         let writer = if self.use_stderr {
diff --git a/src/parse/errors.rs b/src/parse/errors.rs
index bc476ecb6c6..50e8ca59509 100644
--- a/src/parse/errors.rs
+++ b/src/parse/errors.rs
@@ -12,7 +12,7 @@ use crate::{
     build::Arg,
     output::fmt::Colorizer,
     parse::features::suggestions,
-    util::{safe_exit, termcolor::ColorChoice, SUCCESS_CODE, USAGE_CODE},
+    util::{color::ColorChoice, safe_exit, SUCCESS_CODE, USAGE_CODE},
     App, AppSettings,
 };
 
@@ -546,7 +546,7 @@ impl Error {
         other: Option<String>,
         usage: String,
     ) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
         let arg = arg.to_string();
 
         start_error(&mut c, "The argument '");
@@ -582,7 +582,7 @@ impl Error {
     }
 
     pub(crate) fn empty_value(app: &App, arg: &Arg, usage: String) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
         let arg = arg.to_string();
 
         start_error(&mut c, "The argument '");
@@ -601,7 +601,7 @@ impl Error {
     }
 
     pub(crate) fn no_equals(app: &App, arg: String, usage: String) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
 
         start_error(&mut c, "Equal sign is needed when assigning values to '");
         c.warning(&arg);
@@ -629,7 +629,7 @@ impl Error {
     where
         G: AsRef<str> + Display,
     {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
         let suffix = suggestions::did_you_mean(&bad_val, good_vals.iter()).pop();
 
         let mut sorted: Vec<String> = good_vals
@@ -690,7 +690,7 @@ impl Error {
         name: String,
         usage: String,
     ) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
 
         start_error(&mut c, "The subcommand '");
         c.warning(subcmd.clone());
@@ -716,7 +716,7 @@ impl Error {
     }
 
     pub(crate) fn unrecognized_subcommand(app: &App, subcmd: String, name: String) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
 
         start_error(&mut c, " The subcommand '");
         c.warning(subcmd.clone());
@@ -739,7 +739,7 @@ impl Error {
         required: Vec<String>,
         usage: String,
     ) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
 
         start_error(
             &mut c,
@@ -766,7 +766,7 @@ impl Error {
     }
 
     pub(crate) fn missing_subcommand(app: &App, name: String, usage: String) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
 
         start_error(&mut c, "'");
         c.warning(name);
@@ -784,7 +784,7 @@ impl Error {
     }
 
     pub(crate) fn invalid_utf8(app: &App, usage: String) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
 
         start_error(
             &mut c,
@@ -809,7 +809,7 @@ impl Error {
         curr_occurs: usize,
         usage: String,
     ) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
         let verb = Error::singular_or_plural(curr_occurs);
 
         start_error(&mut c, "The argument '");
@@ -836,7 +836,7 @@ impl Error {
     }
 
     pub(crate) fn too_many_values(app: &App, val: String, arg: String, usage: String) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
 
         start_error(&mut c, "The value '");
         c.warning(val.clone());
@@ -862,7 +862,7 @@ impl Error {
         curr_vals: usize,
         usage: String,
     ) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
         let verb = Error::singular_or_plural(curr_vals);
 
         start_error(&mut c, "The argument '");
@@ -896,7 +896,7 @@ impl Error {
             info,
             source,
             backtrace,
-        } = Self::value_validation_with_color(arg, val, err, app.color());
+        } = Self::value_validation_with_color(arg, val, err, app.get_color());
         try_help(app, &mut message);
         Self {
             message,
@@ -947,7 +947,7 @@ impl Error {
         curr_vals: usize,
         usage: String,
     ) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
         let verb = Error::singular_or_plural(curr_vals);
 
         start_error(&mut c, "The argument '");
@@ -970,7 +970,7 @@ impl Error {
     }
 
     pub(crate) fn unexpected_multiple_usage(app: &App, arg: &Arg, usage: String) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
         let arg = arg.to_string();
 
         start_error(&mut c, "The argument '");
@@ -994,7 +994,7 @@ impl Error {
         did_you_mean: Option<(String, Option<String>)>,
         usage: String,
     ) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
 
         start_error(&mut c, "Found argument '");
         c.warning(arg.clone());
@@ -1039,7 +1039,7 @@ impl Error {
     }
 
     pub(crate) fn unnecessary_double_dash(app: &App, arg: String, usage: String) -> Self {
-        let mut c = Colorizer::new(true, app.color());
+        let mut c = Colorizer::new(true, app.get_color());
 
         start_error(&mut c, "Found argument '");
         c.warning(arg.clone());
diff --git a/src/parse/parser.rs b/src/parse/parser.rs
index 143dc418fe3..aa5b26554ed 100644
--- a/src/parse/parser.rs
+++ b/src/parse/parser.rs
@@ -1874,7 +1874,7 @@ impl<'help, 'app> Parser<'help, 'app> {
     }
 
     pub(crate) fn write_help_err(&self) -> ClapResult<Colorizer> {
-        let mut c = Colorizer::new(true, self.app.color());
+        let mut c = Colorizer::new(true, self.app.get_color());
         Help::new(HelpWriter::Buffer(&mut c), self, false).write_help()?;
         Ok(c)
     }
@@ -1886,7 +1886,7 @@ impl<'help, 'app> Parser<'help, 'app> {
         );
 
         use_long = use_long && self.use_long_help();
-        let mut c = Colorizer::new(false, self.app.color());
+        let mut c = Colorizer::new(false, self.app.get_color());
 
         match Help::new(HelpWriter::Buffer(&mut c), self, use_long).write_help() {
             Err(e) => e.into(),
@@ -1898,7 +1898,7 @@ impl<'help, 'app> Parser<'help, 'app> {
         debug!("Parser::version_err");
 
         let msg = self.app._render_version(use_long);
-        let mut c = Colorizer::new(false, self.app.color());
+        let mut c = Colorizer::new(false, self.app.get_color());
         c.none(msg);
         ClapError::new(c, ErrorKind::DisplayVersion)
     }
diff --git a/src/util/color.rs b/src/util/color.rs
new file mode 100644
index 00000000000..825b98760b9
--- /dev/null
+++ b/src/util/color.rs
@@ -0,0 +1,73 @@
+/// Represents the color preferences for program output
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub enum ColorChoice {
+    /// Enables colored output only when the output is going to a terminal or TTY.
+    ///
+    /// **NOTE:** This is the default behavior of `clap`.
+    ///
+    /// # Platform Specific
+    ///
+    /// This setting only applies to Unix, Linux, and macOS (i.e. non-Windows platforms).
+    ///
+    /// # Examples
+    ///
+    #[cfg_attr(not(feature = "color"), doc = " ```ignore")]
+    #[cfg_attr(feature = "color", doc = " ```no_run")]
+    /// # use clap::{App, ColorChoice};
+    /// App::new("myprog")
+    ///     .color(ColorChoice::Auto)
+    ///     .get_matches();
+    /// ```
+    Auto,
+
+    /// Enables colored output regardless of whether or not the output is going to a terminal/TTY.
+    ///
+    /// # Platform Specific
+    ///
+    /// This setting only applies to Unix, Linux, and macOS (i.e. non-Windows platforms).
+    ///
+    /// # Examples
+    ///
+    #[cfg_attr(not(feature = "color"), doc = " ```ignore")]
+    #[cfg_attr(feature = "color", doc = " ```no_run")]
+    /// # use clap::{App, ColorChoice};
+    /// App::new("myprog")
+    ///     .color(ColorChoice::Always)
+    ///     .get_matches();
+    /// ```
+    Always,
+
+    /// Disables colored output no matter if the output is going to a terminal/TTY, or not.
+    ///
+    /// # Platform Specific
+    ///
+    /// This setting only applies to Unix, Linux, and macOS (i.e. non-Windows platforms)
+    ///
+    /// # Examples
+    ///
+    #[cfg_attr(not(feature = "color"), doc = " ```ignore")]
+    #[cfg_attr(feature = "color", doc = " ```no_run")]
+    /// # use clap::{App, ColorChoice};
+    /// App::new("myprog")
+    ///     .color(ColorChoice::Never)
+    ///     .get_matches();
+    /// ```
+    Never,
+}
+
+impl Default for ColorChoice {
+    fn default() -> Self {
+        Self::Auto
+    }
+}
+
+#[cfg(feature = "color")]
+pub(crate) use termcolor::Color;
+
+#[cfg(not(feature = "color"))]
+#[derive(Debug)]
+pub(crate) enum Color {
+    Green,
+    Yellow,
+    Red,
+}
diff --git a/src/util/mod.rs b/src/util/mod.rs
index 957a0ae3595..ed35765ff6a 100644
--- a/src/util/mod.rs
+++ b/src/util/mod.rs
@@ -12,11 +12,7 @@ pub use self::fnv::Key;
 pub(crate) use self::str_to_bool::str_to_bool;
 pub(crate) use self::{graph::ChildGraph, id::Id};
 
-#[cfg(feature = "color")]
-pub(crate) use termcolor;
-
-#[cfg(not(feature = "color"))]
-pub(crate) mod termcolor;
+pub(crate) mod color;
 
 pub(crate) const SUCCESS_CODE: i32 = 0;
 // While sysexists.h defines EX_USAGE as 64, this doesn't seem to be used much in practice but
@@ -39,5 +35,6 @@ pub(crate) fn safe_exit(code: i32) -> ! {
 pub(crate) fn eq_ignore_case(left: &str, right: &str) -> bool {
     left.eq_ignore_ascii_case(right)
 }
+
 #[cfg(feature = "unicode")]
 pub(crate) use unicase::eq as eq_ignore_case;
diff --git a/src/util/termcolor.rs b/src/util/termcolor.rs
deleted file mode 100644
index 97ac63f82de..00000000000
--- a/src/util/termcolor.rs
+++ /dev/null
@@ -1,13 +0,0 @@
-#[derive(Debug, Copy, Clone, PartialEq)]
-pub(crate) enum ColorChoice {
-    Auto,
-    Always,
-    Never,
-}
-
-#[derive(Debug)]
-pub(crate) enum Color {
-    Green,
-    Yellow,
-    Red,
-}
diff --git a/tests/help.rs b/tests/help.rs
index dbc3244879e..ebb12f60739 100644
--- a/tests/help.rs
+++ b/tests/help.rs
@@ -2263,13 +2263,11 @@ fn option_usage_order() {
 
 #[test]
 fn about_in_subcommands_list() {
-    let app = App::new("about-in-subcommands-list")
-        .setting(AppSettings::ColorNever)
-        .subcommand(
-            App::new("sub")
-                .long_about("long about sub")
-                .about("short about sub"),
-        );
+    let app = App::new("about-in-subcommands-list").subcommand(
+        App::new("sub")
+            .long_about("long about sub")
+            .about("short about sub"),
+    );
 
     assert!(utils::compare_output(
         app,
diff --git a/tests/macros.rs b/tests/macros.rs
index 1bf90ebc281..5a90d070246 100644
--- a/tests/macros.rs
+++ b/tests/macros.rs
@@ -32,7 +32,7 @@ fn basic() {
         (version: "0.1")
         (about: "tests clap library")
         (author: "Kevin K. <kbknapp@gmail.com>")
-        (@global_setting ColorNever)
+        (@global_setting UnifiedHelpMessage)
         (@arg opt: -o --option +takes_value ... "tests options")
         (@arg positional: index(1) "tests positionals")
         (@arg flag: -f --flag ... +global "tests flags")