Add tk diff --exit-zero flag

That causes `tk diff` to exit with 0 when there is a diff present.

Signed-off-by: Craig Furman <craig.furman89@gmail.com>

cmd/tk/workflow.go

@@ -114,6 +114,7 @@ func diffCmd() *cli.Command {
 	cmd.Flags().StringVar(&opts.Strategy, "diff-strategy", "", "force the diff-strategy to use. Automatically chosen if not set.")
 	cmd.Flags().BoolVarP(&opts.Summarize, "summarize", "s", false, "print summary of the differences, not the actual contents")
 	cmd.Flags().BoolVarP(&opts.WithPrune, "with-prune", "p", false, "include objects deleted from the configuration in the differences")
+	cmd.Flags().BoolVarP(&opts.ExitZero, "exit-zero", "z", false, "Exit with 0 even when differences are found.")
 
 	vars := workflowFlags(cmd.Flags())
 	getJsonnetOpts := jsonnetFlags(cmd.Flags())
@@ -142,7 +143,11 @@ func diffCmd() *cli.Command {
 			return err
 		}
 
-		os.Exit(ExitStatusDiff)
+		exitStatusDiff := ExitStatusDiff
+		if opts.ExitZero {
+			exitStatusDiff = ExitStatusClean
+		}
+		os.Exit(exitStatusDiff)
 		return nil
 	}
 

pkg/tanka/workflow.go

@@ -94,6 +94,8 @@ type DiffOpts struct {
 	Summarize bool
 	// WithPrune includes objects to be deleted by prune command in the diff
 	WithPrune bool
+	// Exit with 0 even when differences are found
+	ExitZero bool
 }
 
 // Diff parses the environment at the given directory (a `baseDir`) and returns