Add feature requirements and example to which_re documentation

src/lib.rs

@@ -9,7 +9,7 @@
 //! use which::which;
 //! use std::path::PathBuf;
 //!
-//! let result = which::which("rustc").unwrap();
+//! let result = which("rustc").unwrap();
 //! assert_eq!(result, PathBuf::from("/usr/bin/rustc"));
 //!
 //! ```
@@ -72,12 +72,16 @@ pub fn which_all<T: AsRef<OsStr>>(binary_name: T) -> Result<impl Iterator<Item =
 
 /// Find all binaries matching a regular expression in a the system PATH.
 ///
+/// Only available when feature `regex` is enabled.
+///
 /// # Arguments
 ///
 /// * `regex` - A regular expression to match binaries with
 ///
 /// # Examples
 ///
+/// Find Python executables:
+///
 /// ```no_run
 /// use regex::Regex;
 /// use which::which;
@@ -88,6 +92,16 @@ pub fn which_all<T: AsRef<OsStr>>(binary_name: T) -> Result<impl Iterator<Item =
 /// let python_paths = vec![PathBuf::from("/usr/bin/python2"), PathBuf::from("/usr/bin/python3")];
 /// assert_eq!(binaries, python_paths);
 /// ```
+///
+/// Find all cargo subcommand executables on the path:
+///
+/// ```
+/// use which::which_re;
+/// use regex::Regex;
+///
+/// which_re(Regex::new("^cargo-.*").unwrap()).unwrap()
+///     .for_each(|pth| println!("{}", pth.to_string_lossy()));
+/// ```
 #[cfg(feature = "regex")]
 pub fn which_re(regex: impl Borrow<Regex>) -> Result<impl Iterator<Item = path::PathBuf>> {
     which_re_in(regex, env::var_os("PATH"))
@@ -106,6 +120,8 @@ where
 
 /// Find all binaries matching a regular expression in a list of paths.
 ///
+/// Only available when feature `regex` is enabled.
+///
 /// # Arguments
 ///
 /// * `regex` - A regular expression to match binaries with