Allow to omit large common parts in diff output

README.md

@@ -182,3 +182,11 @@ The above will install this plugin into your `$HELM_HOME/plugins` directory.
 - You need to have [Go](http://golang.org) installed. Make sure to set `$GOPATH`
 - If you don't have [Glide](http://glide.sh) installed, this will install it into
   `$GOPATH/bin` for you.
+
+### Running Tests
+Automated tests are implemented with [*testing*](https://golang.org/pkg/testing/).
+
+To run all tests:
+```
+go test -v ./...
+```

cmd/revision.go

@@ -17,6 +17,7 @@ type revision struct {
 	client          helm.Interface
 	suppressedKinds []string
 	revisions       []string
+	outputContext   int
 }
 
 const revisionCmdLongUsage = `
@@ -69,6 +70,7 @@ func revisionCmd() *cobra.Command {
 
 	revisionCmd.Flags().BoolP("suppress-secrets", "q", false, "suppress secrets in the output")
 	revisionCmd.Flags().StringArrayVar(&diff.suppressedKinds, "suppress", []string{}, "allows suppression of the values listed in the diff output")
+	revisionCmd.Flags().IntVarP(&diff.outputContext, "context", "C", -1, "output NUM lines of context around changes")
 	revisionCmd.SuggestionsMinimumDistance = 1
 	return revisionCmd
 }
@@ -89,7 +91,7 @@ func (d *revision) differentiate() error {
 			return prettyError(err)
 		}
 
-		diff.DiffManifests(manifest.Parse(revisionResponse.Release.Manifest), manifest.Parse(releaseResponse.Release.Manifest), d.suppressedKinds, os.Stdout)
+		diff.DiffManifests(manifest.Parse(revisionResponse.Release.Manifest), manifest.Parse(releaseResponse.Release.Manifest), d.suppressedKinds, d.outputContext, os.Stdout)
 
 	case 2:
 		revision1, _ := strconv.Atoi(d.revisions[0])
@@ -108,7 +110,7 @@ func (d *revision) differentiate() error {
 			return prettyError(err)
 		}
 
-		diff.DiffManifests(manifest.Parse(revisionResponse1.Release.Manifest), manifest.Parse(revisionResponse2.Release.Manifest), d.suppressedKinds, os.Stdout)
+		diff.DiffManifests(manifest.Parse(revisionResponse1.Release.Manifest), manifest.Parse(revisionResponse2.Release.Manifest), d.suppressedKinds, d.outputContext, os.Stdout)
 
 	default:
 		return errors.New("Invalid Arguments")

cmd/rollback.go

@@ -16,6 +16,7 @@ type rollback struct {
 	client          helm.Interface
 	suppressedKinds []string
 	revisions       []string
+	outputContext   int
 }
 
 const rollbackCmdLongUsage = `
@@ -59,6 +60,7 @@ func rollbackCmd() *cobra.Command {
 
 	rollbackCmd.Flags().BoolP("suppress-secrets", "q", false, "suppress secrets in the output")
 	rollbackCmd.Flags().StringArrayVar(&diff.suppressedKinds, "suppress", []string{}, "allows suppression of the values listed in the diff output")
+	rollbackCmd.Flags().IntVarP(&diff.outputContext, "context", "C", -1, "output NUM lines of context around changes")
 	rollbackCmd.SuggestionsMinimumDistance = 1
 	return rollbackCmd
 }
@@ -80,7 +82,7 @@ func (d *rollback) backcast() error {
 	}
 
 	// create a diff between the current manifest and the version of the manifest that a user is intended to rollback
-	diff.DiffManifests(manifest.Parse(releaseResponse.Release.Manifest), manifest.Parse(revisionResponse.Release.Manifest), d.suppressedKinds, os.Stdout)
+	diff.DiffManifests(manifest.Parse(releaseResponse.Release.Manifest), manifest.Parse(revisionResponse.Release.Manifest), d.suppressedKinds, d.outputContext, os.Stdout)
 
 	return nil
 }

cmd/upgrade.go

@@ -22,6 +22,7 @@ type diffCmd struct {
 	resetValues     bool
 	allowUnreleased bool
 	suppressedKinds []string
+	outputContext   int
 }
 
 const globalUsage = `Show a diff explaining what a helm upgrade would change.
@@ -67,6 +68,7 @@ func newChartCommand() *cobra.Command {
 	f.BoolVar(&diff.resetValues, "reset-values", false, "reset the values to the ones built into the chart and merge in any new values")
 	f.BoolVar(&diff.allowUnreleased, "allow-unreleased", false, "enables diffing of releases that are not yet deployed via Helm")
 	f.StringArrayVar(&diff.suppressedKinds, "suppress", []string{}, "allows suppression of the values listed in the diff output")
+	f.IntVarP(&diff.outputContext, "context", "C", -1, "output NUM lines of context around changes")
 
 	return cmd
 
@@ -137,7 +139,7 @@ func (d *diffCmd) run() error {
 		newSpecs = manifest.Parse(upgradeResponse.Release.Manifest)
 	}
 
-	diff.DiffManifests(currentSpecs, newSpecs, d.suppressedKinds, os.Stdout)
+	diff.DiffManifests(currentSpecs, newSpecs, d.suppressedKinds, d.outputContext, os.Stdout)
 
 	return nil
 }

diff/diff.go

@@ -4,38 +4,39 @@ import (
 	"fmt"
 	"io"
 	"strings"
+	"math"
 
 	"github.com/aryann/difflib"
 	"github.com/mgutz/ansi"
 
 	"github.com/databus23/helm-diff/manifest"
 )
 
-func DiffManifests(oldIndex, newIndex map[string]*manifest.MappingResult, suppressedKinds []string, to io.Writer) {
+func DiffManifests(oldIndex, newIndex map[string]*manifest.MappingResult, suppressedKinds []string, context int, to io.Writer) {
 	for key, oldContent := range oldIndex {
 		if newContent, ok := newIndex[key]; ok {
 			if oldContent.Content != newContent.Content {
 				// modified
 				fmt.Fprintf(to, ansi.Color("%s has changed:", "yellow")+"\n", key)
-				printDiff(suppressedKinds, oldContent.Kind, oldContent.Content, newContent.Content, to)
+				printDiff(suppressedKinds, oldContent.Kind, context, oldContent.Content, newContent.Content, to)
 			}
 		} else {
 			// removed
 			fmt.Fprintf(to, ansi.Color("%s has been removed:", "yellow")+"\n", key)
-			printDiff(suppressedKinds, oldContent.Kind, oldContent.Content, "", to)
+			printDiff(suppressedKinds, oldContent.Kind, context, oldContent.Content, "", to)
 		}
 	}
 
 	for key, newContent := range newIndex {
 		if _, ok := oldIndex[key]; !ok {
 			// added
 			fmt.Fprintf(to, ansi.Color("%s has been added:", "yellow")+"\n", key)
-			printDiff(suppressedKinds, newContent.Kind, "", newContent.Content, to)
+			printDiff(suppressedKinds, newContent.Kind, context, "", newContent.Content, to)
 		}
 	}
 }
 
-func printDiff(suppressedKinds []string, kind, before, after string, to io.Writer) {
+func printDiff(suppressedKinds []string, kind string, context int, before, after string, to io.Writer) {
 	diffs := difflib.Diff(strings.Split(before, "\n"), strings.Split(after, "\n"))
 
 	for _, ckind := range suppressedKinds {
@@ -46,16 +47,71 @@ func printDiff(suppressedKinds []string, kind, before, after string, to io.Write
 		}
 	}
 
-	for _, diff := range diffs {
-		text := diff.Payload
+	if context >= 0 {
+		distances := calculateDistances(diffs)
+		omitting := false
+		for i, diff := range diffs {
+			if distances[i] > context {
+				if !omitting {
+					fmt.Fprintln(to, "...")
+					omitting = true
+				}
+			} else {
+				omitting = false
+				printDiffRecord(diff, to)
+			}
+		}
+	} else {
+		for _, diff := range diffs {
+			printDiffRecord(diff, to)
+		}
+	}
+}
+
+func printDiffRecord(diff difflib.DiffRecord, to io.Writer) {
+	text := diff.Payload
+
+	switch diff.Delta {
+	case difflib.RightOnly:
+		fmt.Fprintf(to, "%s\n", ansi.Color("+ "+text, "green"))
+	case difflib.LeftOnly:
+		fmt.Fprintf(to, "%s\n", ansi.Color("- "+text, "red"))
+	case difflib.Common:
+		fmt.Fprintf(to, "%s\n", "  "+text)
+	}
+}
 
-		switch diff.Delta {
-		case difflib.RightOnly:
-			fmt.Fprintf(to, "%s\n", ansi.Color("+ "+text, "green"))
-		case difflib.LeftOnly:
-			fmt.Fprintf(to, "%s\n", ansi.Color("- "+text, "red"))
-		case difflib.Common:
-			fmt.Fprintf(to, "%s\n", "  "+text)
+// Calculate distance of every diff-line to the closest change
+func calculateDistances(diffs []difflib.DiffRecord) map[int]int {
+	distances := map[int]int{}
+
+	// Iterate forwards through diffs, set 'distance' based on closest 'change' before this line
+	change := -1
+	for i, diff := range diffs {
+		if diff.Delta != difflib.Common {
+			change = i
+		}
+		distance := math.MaxInt32
+		if change != -1 {
+			distance = i - change
+		}
+		distances[i] = distance
+	}
+
+	// Iterate backwards through diffs, reduce 'distance' based on closest 'change' after this line
+	change = -1
+	for i := len(diffs) - 1; i >= 0; i-- {
+		diff := diffs[i]
+		if diff.Delta != difflib.Common {
+			change = i
+		}
+		if change != -1 {
+			distance := change - i
+			if distance < distances[i] {
+				distances[i] = distance
+			}
 		}
 	}
+
+	return distances
 }

diff/diff_test.go

@@ -0,0 +1,123 @@
+package diff
+
+import (
+	"testing"
+	"bytes"
+	"github.com/mgutz/ansi"
+)
+
+var text1 = "" +
+	"line1\n" +
+	"line2\n" +
+	"line3\n" +
+	"line4\n" +
+	"line5\n" +
+	"line6\n" +
+	"line7\n" +
+	"line8\n" +
+	"line9\n" +
+	"line10"
+
+var text2 = "" +
+	"line1 - different!\n" +
+	"line2 - different!\n" +
+	"line3\n" +
+	"line4\n" +
+	"line5\n" +
+	"line6\n" +
+	"line7\n" +
+	"line8 - different!\n" +
+	"line9\n" +
+	"line10"
+
+func TestPrintDiffWithContext(t *testing.T) {
+
+	t.Run("context-disabled", func(t *testing.T) {
+		assertDiff(t, text1, text2, -1, ""+
+			"- line1\n"+
+			"- line2\n"+
+			"+ line1 - different!\n"+
+			"+ line2 - different!\n"+
+			"  line3\n"+
+			"  line4\n"+
+			"  line5\n"+
+			"  line6\n"+
+			"  line7\n"+
+			"- line8\n"+
+			"+ line8 - different!\n"+
+			"  line9\n"+
+			"  line10\n")
+	})
+
+	t.Run("context-0", func(t *testing.T) {
+		assertDiff(t, text1, text2, 0, ""+
+			"- line1\n"+
+			"- line2\n"+
+			"+ line1 - different!\n"+
+			"+ line2 - different!\n"+
+			"...\n"+
+			"- line8\n"+
+			"+ line8 - different!\n"+
+			"...\n")
+	})
+
+	t.Run("context-1", func(t *testing.T) {
+		assertDiff(t, text1, text2, 1, ""+
+			"- line1\n"+
+			"- line2\n"+
+			"+ line1 - different!\n"+
+			"+ line2 - different!\n"+
+			"  line3\n"+
+			"...\n"+
+			"  line7\n"+
+			"- line8\n"+
+			"+ line8 - different!\n"+
+			"  line9\n"+
+			"...\n")
+	})
+
+	t.Run("context-2", func(t *testing.T) {
+		assertDiff(t, text1, text2, 2, ""+
+			"- line1\n"+
+			"- line2\n"+
+			"+ line1 - different!\n"+
+			"+ line2 - different!\n"+
+			"  line3\n"+
+			"  line4\n"+
+			"...\n"+
+			"  line6\n"+
+			"  line7\n"+
+			"- line8\n"+
+			"+ line8 - different!\n"+
+			"  line9\n"+
+			"  line10\n")
+	})
+
+	t.Run("context-3", func(t *testing.T) {
+		assertDiff(t, text1, text2, 3, ""+
+			"- line1\n"+
+			"- line2\n"+
+			"+ line1 - different!\n"+
+			"+ line2 - different!\n"+
+			"  line3\n"+
+			"  line4\n"+
+			"  line5\n"+
+			"  line6\n"+
+			"  line7\n"+
+			"- line8\n"+
+			"+ line8 - different!\n"+
+			"  line9\n"+
+			"  line10\n")
+	})
+
+}
+
+func assertDiff(t *testing.T, before, after string, context int, expected string) {
+	ansi.DisableColors(true)
+	var output bytes.Buffer
+	printDiff([]string{}, "some-resource", context, before, after, &output)
+	actual := output.String()
+	if actual != expected {
+		t.Errorf("Unexpected diff output: \nExpected:\n#%v# \nActual:\n#%v#", expected, actual)
+	}
+}