fix: display color when NO_COLOR is an empty string

Author: acuteenvy

src/bin/bat/app.rs

@@ -207,7 +207,10 @@ impl App {
                 || match self.matches.get_one::<String>("color").map(|s| s.as_str()) {
                     Some("always") => true,
                     Some("never") => false,
-                    Some("auto") => env::var_os("NO_COLOR").is_none() && self.interactive_output,
+                    Some("auto") => {
+                        !env::var_os("NO_COLOR").is_some_and(|x| !x.is_empty())
+                            && self.interactive_output
+                    }
                     _ => unreachable!("other values for --color are not allowed"),
                 },
             paging_mode,

src/bin/bat/clap_app.rs

@@ -19,11 +19,12 @@ static VERSION: Lazy<String> = Lazy::new(|| {
 });
 
 pub fn build_app(interactive_output: bool) -> Command {
-    let color_when = if interactive_output && env::var_os("NO_COLOR").is_none() {
-        ColorChoice::Auto
-    } else {
-        ColorChoice::Never
-    };
+    let color_when =
+        if interactive_output && !env::var_os("NO_COLOR").is_some_and(|x| !x.is_empty()) {
+            ColorChoice::Auto
+        } else {
+            ColorChoice::Never
+        };
 
     let mut app = Command::new(crate_name!())
         .version(VERSION.as_str())