Use presence of non-empty NO_COLOR environment variable to decide if …

…terminal suports ANSI.

src/progress.rs

@@ -11,6 +11,9 @@ use crate::command_line_args::CommandLineArgs;
 const PROGRESS_STYLE: &str =
     "{spinner} [{elapsed_precise}] Commands Done/Total: {pos:>2}/{len:2} {wide_bar} ETA {eta_precise}";
 
+const PROGRESS_STYLE_NO_SPINNER: &str =
+    "[{elapsed_precise}] Commands Done/Total: {pos:>2}/{len:2} {wide_bar} ETA {eta_precise}";
+
 pub struct Progress {
     progress_bar: Option<ProgressBar>,
 }
@@ -20,10 +23,23 @@ impl Progress {
         let progress_bar = if !command_line_args.progress_bar {
             None
         } else {
+            // Terminal supports ANSI formatting if NO_COLOR is unset or empty.
+            // Idea from https://github.com/tokio-rs/tracing/pull/2647
+
+            let terminal_supports_ansi = std::env::var("NO_COLOR").map_or(true, |v| v.is_empty());
+
             let progress_bar = ProgressBar::new(0);
-            progress_bar.enable_steady_tick(Duration::from_millis(100));
+            if terminal_supports_ansi {
+                progress_bar.enable_steady_tick(Duration::from_millis(100));
+            }
+
+            let style = if terminal_supports_ansi {
+                PROGRESS_STYLE
+            } else {
+                PROGRESS_STYLE_NO_SPINNER
+            };
 
-            let style = ProgressStyle::with_template(PROGRESS_STYLE)
+            let style = ProgressStyle::with_template(style)
                 .context("ProgressStyle::with_template error")?;
 
             progress_bar.set_style(style);