Make -u option take no effect and hide from users.

Author: futatuki

src/options.rs

@@ -134,10 +134,11 @@ fn app() -> clap::Command<'static> {
                 .required(false),
         )
         .arg(
-            Arg::new("unified_default")
+            // Dummy 'unified' flag of POSIX/GNU diff utility for svn support:
+            // This takes no effect.
+            Arg::new("nop_unified")
                 .short('u')
-                .conflicts_with("display")
-                .help("Use inline style for display mode.")
+                .hide(true)
         )
         .arg(
             Arg::new("label").short('L')
@@ -555,24 +556,20 @@ pub fn parse_args() -> Mode {
         detect_display_width()
     };
 
-    let display_mode = if matches.is_present("unified_default") {
-        DisplayMode::Inline
-    } else {
-        match matches.value_of("display").expect("display has a default") {
-            "side-by-side" => DisplayMode::SideBySide,
-            "side-by-side-show-both" => DisplayMode::SideBySideShowBoth,
-            "inline" => DisplayMode::Inline,
-            "json" => {
-                if env::var(format!("DFT_UNSTABLE")).is_err() {
-                    eprintln!("JSON output is an unstable feature and its format may change in future. To enable JSON output, set the environment variable DFT_UNSTABLE=yes.");
-                    std::process::exit(EXIT_BAD_ARGUMENTS);
-                }
-
-                DisplayMode::Json
-            }
-            _ => {
-                unreachable!("clap has already validated display")
+    let display_mode = match matches.value_of("display").expect("display has a default") {
+        "side-by-side" => DisplayMode::SideBySide,
+        "side-by-side-show-both" => DisplayMode::SideBySideShowBoth,
+        "inline" => DisplayMode::Inline,
+        "json" => {
+            if env::var(format!("DFT_UNSTABLE")).is_err() {
+                eprintln!("JSON output is an unstable feature and its format may change in future. To enable JSON output, set the environment variable DFT_UNSTABLE=yes.");
+                std::process::exit(EXIT_BAD_ARGUMENTS);
             }
+
+            DisplayMode::Json
+        }
+        _ => {
+            unreachable!("clap has already validated display")
         }
     };