Add docs and use pre-defined colors everywhere

.gitignore

@@ -4,3 +4,4 @@ release-out
 .certs
 .tmp
 *.tmp
+.vscode

README.md

@@ -1,6 +1,6 @@
 [![asciicinema example](https://asciinema.org/a/gPEIEo1NzmDTUu2bEPsUboqmU.png)](https://asciinema.org/a/gPEIEo1NzmDTUu2bEPsUboqmU)
 
-# BuildKit
+# BuildKit <!-- omit in toc -->
 
 [![GoDoc](https://godoc.org/github.com/moby/buildkit?status.svg)](https://godoc.org/github.com/moby/buildkit/client/llb)
 [![Build Status](https://github.com/moby/buildkit/workflows/build/badge.svg)](https://github.com/moby/buildkit/actions?query=workflow%3Abuild)
@@ -213,6 +213,12 @@ See [`frontend/dockerfile/docs/experimental.md`](frontend/dockerfile/docs/experi
 
 By default, the build result and intermediate cache will only remain internally in BuildKit. An output needs to be specified to retrieve the result.
 
+> Color Output Controls
+>
+> `buildctl` has support for modifying the colors that are used to output information to the terminal. You can set the environment varliable `BUILDKIT_COLORS` to something like `run=blue;cancel=yellow;warn=orange;error=red` to set the colors that you would like to use. You can also set `NO_COLOR` to disable colorized output.
+>
+> - [A list of the supported colors](https://github.com/moby/buildkit/blob/master/util/progress/progressui/colors.go).
+
 #### Image/Registry
 
 ```bash

util/progress/progressui/colors.go

@@ -8,7 +8,7 @@ import (
 	"github.com/morikuni/aec"
 )
 
-var rex = regexp.MustCompile("(\\w+)=(\\w+)")
+var rex = regexp.MustCompile(`(\w+)=(\w+)`)
 
 var termColorMap = map[string]aec.ANSI{
 	"default": aec.DefaultF,
@@ -35,7 +35,6 @@ var termColorMap = map[string]aec.ANSI{
 }
 
 func setUserDefinedTermColors(colorsEnv string) {
-
 	data := rex.FindAllStringSubmatch(colorsEnv, -1)
 	for _, kv := range data {
 		k := kv[1]

util/progress/progressui/init.go

@@ -16,30 +16,31 @@ var colorError aec.ANSI
 var envColorString string
 
 func init() {
+	// As recommended on https://no-color.org/
 	_, noColorIsSet = os.LookupEnv("NO_COLOR")
+	// Loosely based on the standard set by Linux LS_COLORS.
 	_, buildkitColorIsSet = os.LookupEnv("BUILDKIT_COLORS")
 
 	if noColorIsSet {
-		colorRun = aec.DefaultF
-		colorCancel = aec.DefaultF
-		colorWarning = aec.DefaultF
-		colorError = aec.DefaultF
+		colorRun = termColorMap["default"]
+		colorCancel = termColorMap["default"]
+		colorWarning = termColorMap["default"]
+		colorError = termColorMap["default"]
 		return
 	} else if runtime.GOOS == "windows" {
-		colorRun = aec.CyanF
-		colorCancel = aec.YellowF
-		colorWarning = aec.Color8BitF(aec.NewRGB8Bit(255, 140, 0))
-		colorError = aec.RedF
+		colorRun = termColorMap["cyan"]
+		colorCancel = termColorMap["yellow"]
+		colorWarning = termColorMap["orange"]
+		colorError = termColorMap["red"]
 	} else {
-		colorRun = aec.BlueF
-		colorCancel = aec.YellowF
-		colorWarning = aec.Color8BitF(aec.NewRGB8Bit(255, 140, 0))
-		colorError = aec.RedF
+		colorRun = termColorMap["blue"]
+		colorCancel = termColorMap["yellow"]
+		colorWarning = termColorMap["orange"]
+		colorError = termColorMap["red"]
 	}
 
 	if buildkitColorIsSet {
 		envColorString = os.Getenv("BUILDKIT_COLORS")
 		setUserDefinedTermColors(envColorString)
 	}
-
 }