feat(kubernetes): diff histogram

cmd/tk/workflow.go

@@ -52,7 +52,7 @@ func applyCmd() *cobra.Command {
 			log.Fatalln("Reconciling:", err)
 		}
 
-		if !diff(desired, false) {
+		if !diff(desired, false, kubernetes.DiffOpts{}) {
 			log.Println("Warning: There are no differences. Your apply may not do anything at all.")
 		}
 
@@ -79,7 +79,14 @@ func diffCmd() *cobra.Command {
 			"flags/diff-strategy": "diffStrategy",
 		},
 	}
-	vars := workflowFlags(cmd.Flags())
+
+	// flags
+	var (
+		vars         = workflowFlags(cmd.Flags())
+		diffStrategy = cmd.Flags().String("diff-strategy", "", "force the diff-strategy to use. Automatically chosen if not set.")
+		summarize    = cmd.Flags().BoolP("summarize", "s", false, "quick summary of the differences, hides file contents")
+	)
+
 	cmd.Run = func(cmd *cobra.Command, args []string) {
 		if kube == nil {
 			log.Fatalln(kubernetes.ErrorMissingConfig{Verb: "diff"})
@@ -91,29 +98,28 @@ func diffCmd() *cobra.Command {
 		}
 
 		if kube.Spec.DiffStrategy == "" {
-			kube.Spec.DiffStrategy = cmd.Flag("diff-strategy").Value.String()
+			kube.Spec.DiffStrategy = *diffStrategy
 		}
 
 		desired, err := kube.Reconcile(raw, stringsToRegexps(vars.targets)...)
 		if err != nil {
 			log.Fatalln("Reconciling:", err)
 		}
 
-		if diff(desired, interactive) {
+		if diff(desired, interactive, kubernetes.DiffOpts{Summarize: *summarize}) {
 			os.Exit(16)
 		}
 		log.Println("No differences.")
 	}
 
-	cmd.Flags().String("diff-strategy", "", "force the diff-strategy to use. Automatically chosen if not set.")
 	return cmd
 }
 
 // computes the diff, prints to screen.
 // set `pager` to false to disable the pager.
 // When non-interactive, no paging happens anyways.
-func diff(state []kubernetes.Manifest, pager bool) (changed bool) {
-	changes, err := kube.Diff(state)
+func diff(state []kubernetes.Manifest, pager bool, opts kubernetes.DiffOpts) (changed bool) {
+	changes, err := kube.Diff(state, opts)
 	if err != nil {
 		log.Fatalln("Diffing:", err)
 	}

pkg/kubernetes/kubernetes.go

@@ -120,8 +120,13 @@ func (k *Kubernetes) Apply(state []Manifest, opts ApplyOpts) error {
 	return k.client.Apply(yaml, k.Spec.Namespace, opts)
 }
 
+// DiffOpts allow to specify additional parameters for diff operations
+type DiffOpts struct {
+	Summarize bool
+}
+
 // Diff takes the desired state and returns the differences from the cluster
-func (k *Kubernetes) Diff(state []Manifest) (*string, error) {
+func (k *Kubernetes) Diff(state []Manifest, opts DiffOpts) (*string, error) {
 	if k == nil {
 		return nil, ErrorMissingConfig{"diff"}
 	}
@@ -139,7 +144,19 @@ func (k *Kubernetes) Diff(state []Manifest) (*string, error) {
 		}
 	}
 
-	return k.differs[k.Spec.DiffStrategy](yaml)
+	d, err := k.differs[k.Spec.DiffStrategy](yaml)
+	switch {
+	case err != nil:
+		return nil, err
+	case d == nil:
+		return nil, nil
+	}
+
+	if opts.Summarize {
+		return diffstat(*d)
+	}
+
+	return d, nil
 }
 
 func objectspec(m Manifest) string {

pkg/kubernetes/util.go

@@ -8,8 +8,11 @@ import (
 	"os/exec"
 	"path/filepath"
 	"regexp"
+	"strings"
 )
 
+// diff computes the differences between the strings `is` and `should` using the
+// UNIX `diff(1)` utility.
 func diff(name, is, should string) (string, error) {
 	dir, err := ioutil.TempDir("", "diff")
 	if err != nil {
@@ -46,6 +49,22 @@ func diff(name, is, should string) (string, error) {
 	return out, nil
 }
 
+// diffstat uses `diffstat(1)` utility to summarize a `diff(1)` output
+func diffstat(d string) (*string, error) {
+	cmd := exec.Command("diffstat", "-C")
+	buf := bytes.Buffer{}
+	cmd.Stdout = &buf
+	cmd.Stderr = os.Stderr
+	cmd.Stdin = strings.NewReader(d)
+
+	if err := cmd.Run(); err != nil {
+		return nil, fmt.Errorf("invoking diffstat(1): %s", err.Error())
+	}
+
+	out := buf.String()
+	return &out, nil
+}
+
 // FilteredErr is a filtered Stderr. If one of the regular expressions match, the current input is discarded.
 type FilteredErr []*regexp.Regexp