feat: Expose ANSI styling to the user

This gives users the control over where clap outputs while still getting
colors.  For users who want to support old windows versions, check out
`fwdansi` crate.

CHANGELOG.md

@@ -272,10 +272,11 @@ Behavior Changes
 - Can now pass runtime generated data to `Command`, `Arg`, `ArgGroup`, `PossibleValue`, etc without managing lifetimes with the `string` feature flag (#2150, #4223)
 - New default `error-context`, `help` and `usage` feature flags that can be turned off for smaller binaries (#4236)
 - *(error)* `Error::apply` for changing the formatter for dropping binary size (#4111)
-- *(error)* `Command::render`
+- *(error)* `Command::render` which can render to plain text or ANSI escape codes
 - *(help)* Show `PossibleValue::help` in long help (`--help`) (#3312)
 - *(help)* New `{tab}` variable for `Command::help_template` (#4161)
-- *(help)* `Command::render_help` and `Command::render_long_help`
+- *(help)* `Command::render_help` and `Command::render_long_help` which can render to plain text or ANSI escape codes
+- *(help)* `Command::render_usage` now returns a `StyledStr` which can render to plain text or ANSI escape codes
 
 ### Fixes
 

src/builder/styled_str.rs

@@ -22,6 +22,12 @@ impl StyledStr {
         }
     }
 
+    /// Display using [ANSI Escape Code](https://en.wikipedia.org/wiki/ANSI_escape_code) styling
+    #[cfg(feature = "color")]
+    pub fn ansi(&self) -> impl std::fmt::Display + '_ {
+        AnsiDisplay { styled: self }
+    }
+
     pub(crate) fn header(&mut self, msg: impl Into<String>) {
         self.stylize_(Some(Style::Header), msg.into());
     }
@@ -289,6 +295,26 @@ impl std::fmt::Display for StyledStr {
     }
 }
 
+#[cfg(feature = "color")]
+struct AnsiDisplay<'s> {
+    styled: &'s StyledStr,
+}
+
+#[cfg(feature = "color")]
+impl std::fmt::Display for AnsiDisplay<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        let mut buffer = termcolor::Buffer::ansi();
+        self.styled
+            .write_colored(&mut buffer)
+            .map_err(|_| std::fmt::Error)?;
+        let buffer = buffer.into_inner();
+        let buffer = String::from_utf8(buffer).map_err(|_| std::fmt::Error)?;
+        std::fmt::Display::fmt(&buffer, f)?;
+
+        Ok(())
+    }
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub(crate) enum Style {
     Header,