feat: Auto-detect term for coloring helm-diff output

Since helm-diff has added an ability to auto-detect the term to decide if it should output with color or not, helmfile had been defaulted to no-color.
This resoloves that, by adding a term-detection logic that is same as helm-diff.

As a part of this work, I have also implemented a new global flag `--color`, which is used for forcing color without relying on the term-detection logic implemented in helmfile or explicitly setting the HELM_DIFF_COLOR envvar. I hope it is useful for folks.

Ref https://github.com/roboll/helmfile/issues/2043

Signed-off-by: Yusuke Kuoka <ykuoka@gmail.com>

main.go

@@ -12,6 +12,7 @@ import (
 	"github.com/roboll/helmfile/pkg/state"
 	"github.com/urfave/cli"
 	"go.uber.org/zap"
+	"golang.org/x/crypto/ssh/terminal"
 )
 
 var logger *zap.SugaredLogger
@@ -76,6 +77,10 @@ func main() {
 			Name:  "debug",
 			Usage: "Enable verbose output for Helm and set log-level to debug, this disables --quiet/-q effect",
 		},
+		cli.BoolFlag{
+			Name:  "color",
+			Usage: "Output with color",
+		},
 		cli.BoolFlag{
 			Name:  "no-color",
 			Usage: "Output without color",
@@ -942,6 +947,22 @@ func (c configImpl) Interactive() bool {
 	return c.c.GlobalBool("interactive")
 }
 
+func (c configImpl) Color() bool {
+	if c := c.c.GlobalBool("color"); c {
+		return c
+	}
+
+	// We replicate the helm-diff behavior in helmfile
+	// because when when helmfile calls helm-diff, helm-diff has no access to term and therefore
+	// we can't rely on helm-diff's ability to auto-detect term for color output.
+	// See https://github.com/roboll/helmfile/issues/2043
+
+	term := terminal.IsTerminal(int(os.Stdout.Fd()))
+	// https://github.com/databus23/helm-diff/issues/281
+	dumb := os.Getenv("TERM") == "dumb"
+	return term && !dumb
+}
+
 func (c configImpl) NoColor() bool {
 	return c.c.GlobalBool("no-color")
 }

pkg/app/app.go

@@ -1259,6 +1259,7 @@ func (a *App) apply(r *Run, c ApplyConfigProvider) (bool, bool, []error) {
 	detailedExitCode := true
 
 	diffOpts := &state.DiffOpts{
+		Color:             c.Color(),
 		NoColor:           c.NoColor(),
 		Context:           c.Context(),
 		Output:            c.DiffOutput(),
@@ -1479,6 +1480,7 @@ func (a *App) diff(r *Run, c DiffConfigProvider) (*string, bool, bool, []error)
 	opts := &state.DiffOpts{
 		Context:           c.Context(),
 		Output:            c.DiffOutput(),
+		Color:             c.Color(),
 		NoColor:           c.NoColor(),
 		Set:               c.Set(),
 		SkipDiffOnInstall: c.SkipDiffOnInstall(),

pkg/app/app_test.go

@@ -2426,6 +2426,10 @@ func (a applyConfig) SuppressDiff() bool {
 	return a.suppressDiff
 }
 
+func (a applyConfig) Color() bool {
+	return false
+}
+
 func (a applyConfig) NoColor() bool {
 	return a.noColor
 }

pkg/app/config.go

@@ -56,6 +56,7 @@ type ApplyConfigProvider interface {
 
 	DetailedExitcode() bool
 
+	Color() bool
 	NoColor() bool
 	Context() int
 	DiffOutput() string
@@ -113,6 +114,7 @@ type DiffConfigProvider interface {
 	IncludeNeeds() bool
 
 	DetailedExitcode() bool
+	Color() bool
 	NoColor() bool
 	Context() int
 	DiffOutput() string

pkg/app/diff_test.go

@@ -93,6 +93,10 @@ func (a diffConfig) SuppressDiff() bool {
 	return a.suppressDiff
 }
 
+func (a diffConfig) Color() bool {
+	return false
+}
+
 func (a diffConfig) NoColor() bool {
 	return a.noColor
 }

pkg/state/state.go

@@ -1718,6 +1718,8 @@ func (st *HelmState) prepareDiffReleases(helm helmexec.Interface, additionalValu
 
 				if opts.NoColor {
 					flags = append(flags, "--no-color")
+				} else if opts.Color {
+					flags = append(flags, "--color")
 				}
 
 				if opts.Context > 0 {
@@ -1802,8 +1804,13 @@ func (st *HelmState) createHelmContextWithWriter(spec *ReleaseSpec, w io.Writer)
 }
 
 type DiffOpts struct {
-	Context           int
-	Output            string
+	Context int
+	Output  string
+	// Color forces the color output on helm-diff.
+	// This takes effect only when NoColor is false.
+	Color bool
+	// NoColor forces disabling the color output on helm-diff.
+	// If this is true, Color has no effect.
 	NoColor           bool
 	Set               []string
 	SkipCleanup       bool