feat(cli): Add NO_COLOR support (#779)

.clippy-lints

@@ -1,4 +1,3 @@
--D clippy::all
 -W clippy::nursery
 -W clippy::pedantic
 -A clippy::module-name-repetitions
@@ -10,3 +9,4 @@
 -A clippy::default-trait-access
 -A clippy::enum-glob-use
 -A clippy::option-if-let-else
+-A clippy::blocks-in-conditions

crates/cli/src/args.rs

@@ -680,6 +680,8 @@ pub struct Args {
 	pub notify: bool,
 
 	/// When to use terminal colours
+	///
+	/// Setting the environment variable `NO_COLOR` to any value is equivalent to `--color=never`.
 	#[arg(
 		long,
 		help_heading = OPTSET_OUTPUT,
@@ -1104,6 +1106,11 @@ pub fn get_args() -> Args {
 	debug!("parsing arguments");
 	let mut args = Args::parse_from(args);
 
+	// https://no-color.org/
+	if args.color == ColourMode::Auto && std::env::var("NO_COLOR").is_ok() {
+		args.color = ColourMode::Never;
+	}
+
 	if args.ignore_nothing {
 		args.no_global_ignore = true;
 		args.no_vcs_ignore = true;

doc/watchexec.1

@@ -385,6 +385,8 @@ With this, Watchexec will emit a desktop notification when a command starts and
 .TP
 \fB\-\-color\fR=\fIMODE\fR [default: auto]
 When to use terminal colours
+
+Setting the environment variable `NO_COLOR` to any value is equivalent to `\-\-color=never`.
 .TP
 \fB\-\-timings\fR
 Print how long the command took to run

doc/watchexec.1.md

@@ -536,6 +536,9 @@ may silently do nothing, or log a warning.
 
 :   When to use terminal colours
 
+Setting the environment variable \`NO_COLOR\` to any value is equivalent
+to \`\--color=never\`.
+
 **\--timings**
 
 :   Print how long the command took to run