feat(diff,apply): --context=N for limiting diff context (#849)

Resolves #787

pkg/app/config.go

@@ -41,6 +41,7 @@ type ApplyConfigProvider interface {
 	SuppressSecrets() bool
 
 	NoColor() bool
+	Context() int
 
 	concurrencyConfig
 	interactive
@@ -67,6 +68,7 @@ type DiffConfigProvider interface {
 
 	DetailedExitcode() bool
 	NoColor() bool
+	Context() int
 
 	concurrencyConfig
 }

pkg/app/run.go

@@ -139,6 +139,7 @@ func (r *Run) Apply(c ApplyConfigProvider) []error {
 
 	diffOpts := &state.DiffOpts{
 		NoColor: c.NoColor(),
+		Context: c.Context(),
 	}
 
 	releases, errs := st.DiffReleases(helm, c.Values(), c.Concurrency(), detailedExitCode, c.SuppressSecrets(), false, diffOpts)

pkg/state/state.go

@@ -776,6 +776,10 @@ func (st *HelmState) prepareDiffReleases(helm helmexec.Interface, additionalValu
 					flags = append(flags, "--no-color")
 				}
 
+				if opts.Context > 0 {
+					flags = append(flags, "--context", fmt.Sprintf("%d", opts.Context))
+				}
+
 				if len(errs) > 0 {
 					rsErrs := make([]*ReleaseError, len(errs))
 					for i, e := range errs {
@@ -823,6 +827,7 @@ func (st *HelmState) createHelmContext(spec *ReleaseSpec, workerIndex int) helme
 
 type DiffOpts struct {
 	NoColor bool
+	Context int
 }
 
 func (o *DiffOpts) Apply(opts *DiffOpts) {