Add --append-hash flag to kubectl create configmap/secret

Specifying this new flag will automatically hash the configmap/secret
contents with sha256 and append the first 40 hex-encoded bits of the
hash to the name of the configmap/secret. This is especially useful for
workflows that generate configmaps/secrets from files (e.g.
--from-file).

Note that vowels and vowel-like characters in the hash are remapped to
consonants to make it more difficult to accidentally form bad words.

See this Google doc for more background:
https://docs.google.com/document/d/1x1fJ3pGRx20ujR-Y89HUAw8glUL8-ygaztLkkmQeCdU/edit

pkg/kubectl/configmap.go

@@ -26,6 +26,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/validation"
 	"k8s.io/kubernetes/pkg/api"
+	"k8s.io/kubernetes/pkg/kubectl/util/hash"
 )
 
 // ConfigMapGeneratorV1 supports stable generation of a configMap.
@@ -40,6 +41,8 @@ type ConfigMapGeneratorV1 struct {
 	LiteralSources []string
 	// EnvFileSource to derive the configMap from (optional)
 	EnvFileSource string
+	// AppendHash; if true, derive a hash from the ConfigMap and append it to the name
+	AppendHash bool
 }
 
 // Ensure it supports the generator pattern that uses parameter injection.
@@ -73,14 +76,6 @@ func (s ConfigMapGeneratorV1) Generate(genericParams map[string]interface{}) (ru
 		delegate.LiteralSources = fromLiteralArray
 		delete(genericParams, "from-literal")
 	}
-	params := map[string]string{}
-	for key, value := range genericParams {
-		strVal, isString := value.(string)
-		if !isString {
-			return nil, fmt.Errorf("expected string, saw %v for '%s'", value, key)
-		}
-		params[key] = strVal
-	}
 	fromEnvFileString, found := genericParams["from-env-file"]
 	if found {
 		fromEnvFile, isString := fromEnvFileString.(string)
@@ -90,8 +85,26 @@ func (s ConfigMapGeneratorV1) Generate(genericParams map[string]interface{}) (ru
 		delegate.EnvFileSource = fromEnvFile
 		delete(genericParams, "from-env-file")
 	}
+	hashParam, found := genericParams["append-hash"]
+	if found {
+		hashBool, isBool := hashParam.(bool)
+		if !isBool {
+			return nil, fmt.Errorf("expected bool, found :%v", hashParam)
+		}
+		delegate.AppendHash = hashBool
+		delete(genericParams, "append-hash")
+	}
+	params := map[string]string{}
+	for key, value := range genericParams {
+		strVal, isString := value.(string)
+		if !isString {
+			return nil, fmt.Errorf("expected string, saw %v for '%s'", value, key)
+		}
+		params[key] = strVal
+	}
 	delegate.Name = params["name"]
 	delegate.Type = params["type"]
+
 	return delegate.StructuredGenerate()
 }
 
@@ -104,6 +117,7 @@ func (s ConfigMapGeneratorV1) ParamNames() []GeneratorParam {
 		{"from-literal", false},
 		{"from-env-file", false},
 		{"force", false},
+		{"hash", false},
 	}
 }
 
@@ -130,6 +144,13 @@ func (s ConfigMapGeneratorV1) StructuredGenerate() (runtime.Object, error) {
 			return nil, err
 		}
 	}
+	if s.AppendHash {
+		h, err := hash.ConfigMapHash(configMap)
+		if err != nil {
+			return nil, err
+		}
+		configMap.Name = fmt.Sprintf("%s-%s", configMap.Name, h)
+	}
 	return configMap, nil
 }