ripgrep: add --pcre2-version flag

This flag will output details about the version of PCRE2 that ripgrep
is using (if any).

src/main.rs

@@ -39,6 +39,7 @@ fn try_main(args: Args) -> Result<()> {
             Files => files(&args),
             FilesParallel => files_parallel(&args),
             Types => types(&args),
+            PCRE2Version => pcre2_version(&args),
         }?;
     if matched && (args.quiet() || !messages::errored()) {
         process::exit(0)
@@ -275,3 +276,30 @@ fn types(args: &Args) -> Result<bool> {
     }
     Ok(count > 0)
 }
+
+/// The top-level entry point for --pcre2-version.
+fn pcre2_version(args: &Args) -> Result<bool> {
+    #[cfg(feature = "pcre2")]
+    fn imp(args: &Args) -> Result<bool> {
+        use grep::pcre2;
+
+        let mut stdout = args.stdout();
+
+        let (major, minor) = pcre2::version();
+        writeln!(stdout, "PCRE2 {}.{} is available", major, minor)?;
+
+        if cfg!(target_pointer_width = "64") && pcre2::is_jit_available() {
+            writeln!(stdout, "JIT is available")?;
+        }
+        Ok(true)
+    }
+
+    #[cfg(not(feature = "pcre2"))]
+    fn imp(args: &Args) -> Result<bool> {
+        let mut stdout = args.stdout();
+        writeln!(stdout, "PCRE2 is not available in this build of ripgrep.")?;
+        Ok(false)
+    }
+
+    imp(args)
+}