Print non-printable characters using caret notation (#2443)

When the new flag is set, non-printable characters are printed using caret notation.

src/bin/bat/app.rs

@@ -21,7 +21,7 @@ use bat::{
     input::Input,
     line_range::{HighlightedLineRanges, LineRange, LineRanges},
     style::{StyleComponent, StyleComponents},
-    MappingTarget, PagingMode, SyntaxMapping, WrappingMode,
+    MappingTarget, NonprintableNotation, PagingMode, SyntaxMapping, WrappingMode,
 };
 
 fn is_truecolor_terminal() -> bool {
@@ -173,6 +173,15 @@ impl App {
                     }
                 }),
             show_nonprintable: self.matches.get_flag("show-all"),
+            nonprintable_notation: match self
+                .matches
+                .get_one::<String>("nonprintable-notation")
+                .map(|s| s.as_str())
+            {
+                Some("unicode") => NonprintableNotation::Unicode,
+                Some("caret") => NonprintableNotation::Caret,
+                _ => unreachable!("other values for --nonprintable-notation are not allowed"),
+            },
             wrapping_mode: if self.interactive_output || maybe_term_width.is_some() {
                 if !self.matches.get_flag("chop-long-lines") {
                     match self.matches.get_one::<String>("wrap").map(|s| s.as_str()) {

src/bin/bat/clap_app.rs

@@ -59,6 +59,22 @@ pub fn build_app(interactive_output: bool) -> Command {
                      Use '--tabs' to control the width of the tab-placeholders.",
                 ),
         )
+        .arg(
+            Arg::new("nonprintable-notation")
+                .long("nonprintable-notation")
+                .action(ArgAction::Set)
+                .default_value("unicode")
+                .value_parser(["unicode", "caret"])
+                .value_name("notation")
+                .hide_default_value(true)
+                .help("Set notation for non-printable characters.")
+                .long_help(
+                    "Set notation for non-printable characters.\n\n\
+                    Possible values:\n  \
+                    * unicode (␇, ␊, ␀, ..)\n  \
+                    * caret   (^G, ^J, ^@, ..)",
+                ),
+        )
         .arg(
             Arg::new("plain")
                 .overrides_with("plain")