Try to detect color support, make color configurable

This commit tries to detect if users can render colors in their terminal
and only enables color logs if that is true.

It also adds no-color.org's NO_COLOR env var support to allow it to be
disabled.

cmd/headscale/headscale.go

@@ -4,6 +4,7 @@ import (
 	"os"
 	"time"
 
+	"github.com/efekarakus/termcolor"
 	"github.com/juanfont/headscale/cmd/headscale/cli"
 	"github.com/rs/zerolog"
 	"github.com/rs/zerolog/log"
@@ -11,10 +12,32 @@ import (
 )
 
 func main() {
+	var colors bool
+	switch l := termcolor.SupportLevel(os.Stderr); l {
+	case termcolor.Level16M:
+		colors = true
+	case termcolor.Level256:
+		colors = true
+	case termcolor.LevelBasic:
+		colors = true
+	default:
+		// no color, return text as is.
+		log.Trace().Msg("Colors are not supported, disabling")
+		colors = false
+	}
+
+	// Adhere to no-color.org manifesto of allowing users to
+	// turn off color in cli/services
+	if _, noColorIsSet := os.LookupEnv("NO_COLOR"); noColorIsSet {
+		log.Trace().Msg("NO_COLOR is set, disabling colors")
+		colors = false
+	}
+
 	zerolog.TimeFieldFormat = zerolog.TimeFormatUnix
 	log.Logger = log.Output(zerolog.ConsoleWriter{
 		Out:        os.Stdout,
 		TimeFormat: time.RFC3339,
+		NoColor:    !colors,
 	})
 
 	err := cli.LoadConfig("")

go.mod

@@ -4,6 +4,7 @@ go 1.16
 
 require (
 	github.com/AlecAivazis/survey/v2 v2.0.5
+	github.com/efekarakus/termcolor v1.0.1 // indirect
 	github.com/gin-gonic/gin v1.7.2
 	github.com/hako/durafmt v0.0.0-20210608085754-5c1018a4e16b
 	github.com/klauspost/compress v1.13.1

go.sum

@@ -146,6 +146,8 @@ github.com/eapache/go-resiliency v1.1.0/go.mod h1:kFI+JgMyC7bLPUVY133qvEBtVayf5m
 github.com/eapache/go-xerial-snappy v0.0.0-20180814174437-776d5712da21/go.mod h1:+020luEh2TKB4/GOp8oxxtq0Daoen/Cii55CzbTV6DU=
 github.com/eapache/queue v1.1.0/go.mod h1:6eCeP0CKFpHLu8blIFXhExK/dRa7WDZfr6jVFPTqq+I=
 github.com/edsrzf/mmap-go v1.0.0/go.mod h1:YO35OhQPt3KJa3ryjFM5Bs14WD66h8eGKpfaBNrHW5M=
+github.com/efekarakus/termcolor v1.0.1 h1:YAKFO3bnLrqZGTWyNLcYoSIAQFKVOmbqmDnwsU/znzg=
+github.com/efekarakus/termcolor v1.0.1/go.mod h1:AitrZNrE4nPO538fRsqf+p0WgLdAsGN5pUNrHEPsEMM=
 github.com/emirpasic/gods v1.12.0/go.mod h1:YfzfFFoVP/catgzJb4IKIqXjX78Ha8FMSDh3ymbK86o=
 github.com/envoyproxy/go-control-plane v0.6.9/go.mod h1:SBwIajubJHhxtWwsL9s8ss4safvEdbitLhGGK48rN6g=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
@@ -532,6 +534,7 @@ github.com/mattn/go-isatty v0.0.5/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hd
 github.com/mattn/go-isatty v0.0.7/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
 github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
 github.com/mattn/go-isatty v0.0.9/go.mod h1:YNRxwqDuOph6SZLI9vUUz6OYw3QyUt7WiY2yME+cCiQ=
+github.com/mattn/go-isatty v0.0.10/go.mod h1:qgIWMr58cqv1PHHyhnkY9lrL7etaEgOFcMEpPG5Rm84=
 github.com/mattn/go-isatty v0.0.11/go.mod h1:PhnuNfih5lzO57/f3n+odYbM4JtupLOxQOAqxQCu2WE=
 github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHXY=
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
@@ -1002,6 +1005,7 @@ golang.org/x/sys v0.0.0-20191001151750-bb3f8db39f24/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20191005200804-aed5e4c7ecf9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20191113165036-4c7a9d0fe056/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191120155948-bd437916bb0e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191220142924-d4481acd189f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=