pkg: prepend library when using registry mirror

Signed-off-by: Yoan Blanc <yoan@dosimple.ch>

README.md

@@ -325,7 +325,7 @@ Before executing a command, kaniko checks the cache for the layer.
 If it exists, kaniko will pull and extract the cached layer instead of executing the command.
 If not, kaniko will execute the command and then push the newly created layer to the cache.
 
-Users can opt into caching by setting the `--cache=true` flag.
+Users can opt into caching by setting the `--cache` flag.
 A remote repository for storing cached layers can be provided via the `--cache-repo` flag.
 If this flag isn't provided, a cached repo will be inferred from the `--destination` provided.
 
@@ -341,7 +341,7 @@ docker run -v $(pwd):/workspace gcr.io/kaniko-project/warmer:latest --cache-dir=
 
 `--image` can be specified for any number of desired images.
 This command will cache those images by digest in a local directory named `cache`.
-Once the cache is populated, caching is opted into with the same `--cache=true` flag as above.
+Once the cache is populated, caching is opted into with the same `--cache` flag as above.
 The location of the local cache is provided via the `--cache-dir` flag, defaulting to `/cache` as with the cache warmer.
 See the `examples` directory for how to use with kubernetes clusters and persistent cache volumes.
 
@@ -441,13 +441,13 @@ You can set it multiple times for multiple arguments.
 
 #### --cache
 
-Set this flag as `--cache=true` to opt into caching with kaniko.
+Set this flag as `--cache` to opt into caching with kaniko.
 
 #### --cache-dir
 
 Set this flag to specify a local directory cache for base images. Defaults to `/cache`.
 
-_This flag must be used in conjunction with the `--cache=true` flag._
+_This flag must be used in conjunction with the `--cache` flag._
 
 #### --cache-repo
 
@@ -456,7 +456,7 @@ Set this flag to specify a remote repository that will be used to store cached l
 If this flag is not provided, a cache repo will be inferred from the `--destination` flag.
 If `--destination=gcr.io/kaniko-project/test`, then cached layers will be stored in `gcr.io/kaniko-project/test/cache`.
 
-_This flag must be used in conjunction with the `--cache=true` flag._
+_This flag must be used in conjunction with the `--cache` flag._
 
 #### --context-sub-path
 

cmd/executor/cmd/root.go

@@ -183,7 +183,7 @@ func cacheFlagsValid() error {
 	if !opts.Cache {
 		return nil
 	}
-	// If --cache=true and --no-push=true, then cache repo must be provided
+	// If --cache and --no-push, then cache repo must be provided
 	// since cache can't be inferred from destination
 	if opts.CacheRepo == "" && opts.NoPush {
 		return errors.New("if using cache with --no-push, specify cache repo with --cache-repo")

integration/images.go

@@ -358,7 +358,7 @@ func (d *DockerFileBuilder) buildCachedImages(config *integrationTestConfig, cac
 	_, ex, _, _ := runtime.Caller(0)
 	cwd := filepath.Dir(ex)
 
-	cacheFlag := "--cache=true"
+	cacheFlag := "--cache"
 
 	for dockerfile := range d.TestCacheDockerfiles {
 		benchmarkEnv := "BENCHMARK_FILE=false"

pkg/util/image_util.go

@@ -22,6 +22,7 @@ import (
 	"net/http"
 	"path/filepath"
 	"strconv"
+	"strings"
 
 	"github.com/GoogleContainerTools/kaniko/pkg/timing"
 
@@ -118,6 +119,13 @@ func remoteImage(image string, opts *config.KanikoOptions) (v1.Image, error) {
 			return nil, err
 		}
 
+		if !strings.ContainsRune(image, '/') {
+			ref, err = name.ParseReference("library/"+image, name.WeakValidation)
+			if err != nil {
+				return nil, err
+			}
+		}
+
 		toSet = true
 	}