Don't use colors when stdout or stderr are being redirected

Cargo.lock

@@ -8,6 +8,17 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
 
+[[package]]
+name = "atty"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "winapi",
+]
+
 [[package]]
 name = "autocfg"
 version = "1.0.1"
@@ -104,6 +115,15 @@ dependencies = [
  "wasi",
 ]
 
+[[package]]
+name = "hermit-abi"
+version = "0.1.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62b467343b94ba476dcb2500d242dadbb39557df889310ac77c5d99100aaac33"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.4.0"
@@ -152,6 +172,7 @@ dependencies = [
 name = "ouch"
 version = "0.1.6"
 dependencies = [
+ "atty",
  "bzip2",
  "flate2",
  "lazy_static",

Cargo.toml

@@ -13,6 +13,7 @@ description = "A command-line utility for easily compressing and decompressing f
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+atty        = "0.2.14"
 lazy_static = "1.4.0"
 walkdir     = "2.3.2"
 strsim      = "0.10.0"

src/lib.rs

@@ -29,7 +29,7 @@ lazy_static! {
     static ref NO_COLOR_IS_SET: bool = {
         use std::env;
 
-        env::var("NO_COLOR").is_ok()
+        env::var("NO_COLOR").is_ok() || atty::isnt(atty::Stream::Stdout) || atty::isnt(atty::Stream::Stderr)
     };
 }
 

src/utils.rs

@@ -91,7 +91,7 @@ pub mod colors {
 #[allow(dead_code, non_upper_case_globals)]
 #[cfg(not(target_family = "unix"))]
 pub mod colors {
-    pub fn empty() -> &'static str {
+    pub const fn empty() -> &'static str {
         ""
     }
     pub const reset: fn() -> &'static str = empty;