all: disable log message colors outside of geth

Also tweak behaviour so colors are only enabled when stderr is a terminal.

internal/debug/flags.go

@@ -18,12 +18,15 @@ package debug
 
 import (
 	"fmt"
+	"io"
 	"net/http"
 	_ "net/http/pprof"
 	"os"
 	"runtime"
 
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/log/term"
+	colorable "github.com/mattn/go-colorable"
 	"gopkg.in/urfave/cli.v1"
 )
 
@@ -87,16 +90,22 @@ var Flags = []cli.Flag{
 	memprofilerateFlag, blockprofilerateFlag, cpuprofileFlag, traceFlag,
 }
 
-// glogger is the glog handler used by Geth, allowing the debug APIs to modify
-// verbosity levels, vmodules and backtrace locations.
-var glogger = log.NewGlogHandler(log.StreamHandler(os.Stderr, log.TerminalFormat()))
+var glogger *log.GlogHandler
+
+func init() {
+	usecolor := term.IsTty(os.Stderr.Fd()) && os.Getenv("TERM") != "dumb"
+	output := io.Writer(os.Stderr)
+	if usecolor {
+		output = colorable.NewColorableStderr()
+	}
+	glogger = log.NewGlogHandler(log.StreamHandler(output, log.TerminalFormat(usecolor)))
+}
 
 // Setup initializes profiling and logging based on the CLI flags.
 // It should be called as early as possible in the program.
 func Setup(ctx *cli.Context) error {
 	// logging
 	log.PrintOrigins(ctx.GlobalBool(debugFlag.Name))
-
 	glogger.Verbosity(log.Lvl(ctx.GlobalInt(verbosityFlag.Name)))
 	glogger.Vmodule(ctx.GlobalString(vmoduleFlag.Name))
 	glogger.BacktraceAt(ctx.GlobalString(backtraceAtFlag.Name))