Fix bugs with .dockerignore and improve integration test

I improved handling of the .dockerignore file by:

1. Using docker's parser to parse the .dockerignore and using their
helper functions to determine if a file should be deleted
2. Copying the Dockerfile we are building to /kaniko/Dockerfile so that
if the Dockerfile is specified in .dockerignore it won't be deleted, and
if it is specified in the .dockerignore it won't end up in the final
image
3. I also improved the integration test to create a temp directory with
files to ignore, and updated the .dockerignore to include exclusions (!)

cmd/executor/cmd/root.go

@@ -28,6 +28,7 @@ import (
 	"github.com/GoogleContainerTools/kaniko/pkg/dockerfile"
 	"github.com/GoogleContainerTools/kaniko/pkg/executor"
 	"github.com/GoogleContainerTools/kaniko/pkg/util"
+	"github.com/docker/docker/pkg/fileutils"
 	"github.com/genuinetools/amicontained/container"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -62,10 +63,10 @@ var RootCmd = &cobra.Command{
 		if err := resolveSourceContext(); err != nil {
 			return errors.Wrap(err, "error resolving source context")
 		}
-		if err := removeIgnoredFiles(); err != nil {
-			return errors.Wrap(err, "error removing .dockerignore files from build context")
+		if err := resolveDockerfilePath(); err != nil {
+			return errors.Wrap(err, "error resolving dockerfile path")
 		}
-		return resolveDockerfilePath()
+		return removeIgnoredFiles()
 	},
 	Run: func(cmd *cobra.Command, args []string) {
 		if !checkContained() {
@@ -144,7 +145,7 @@ func resolveDockerfilePath() error {
 			return errors.Wrap(err, "getting absolute path for dockerfile")
 		}
 		opts.DockerfilePath = abs
-		return nil
+		return copyDockerfile()
 	}
 	// Otherwise, check if the path relative to the build context exists
 	if util.FilepathExists(filepath.Join(opts.SrcContext, opts.DockerfilePath)) {
@@ -153,11 +154,21 @@ func resolveDockerfilePath() error {
 			return errors.Wrap(err, "getting absolute path for src context/dockerfile path")
 		}
 		opts.DockerfilePath = abs
-		return nil
+		return copyDockerfile()
 	}
 	return errors.New("please provide a valid path to a Dockerfile within the build context with --dockerfile")
 }
 
+// copy Dockerfile to /kaniko/Dockerfile so that if it's specified in the .dockerignore
+// it won't be copied into the image
+func copyDockerfile() error {
+	if err := util.CopyFile(opts.DockerfilePath, constants.DockerfilePath); err != nil {
+		return errors.Wrap(err, "copying dockerfile")
+	}
+	opts.DockerfilePath = constants.DockerfilePath
+	return nil
+}
+
 // resolveSourceContext unpacks the source context if it is a tar in a bucket
 // it resets srcContext to be the path to the unpacked build context within the image
 func resolveSourceContext() error {
@@ -197,33 +208,18 @@ func removeIgnoredFiles() error {
 		return err
 	}
 	logrus.Infof("Removing ignored files from build context: %s", ignore)
-	for r, i := range ignore {
-		ignore[r] = filepath.Clean(filepath.Join(opts.SrcContext, i))
+	files, err := util.RelativeFiles("", opts.SrcContext)
+	if err != nil {
+		return errors.Wrap(err, "getting all files in src context")
 	}
-	// remove all files in .dockerignore
-	return filepath.Walk(opts.SrcContext, func(path string, fi os.FileInfo, _ error) error {
-		if ignoreFile(path, ignore) {
-			if err := os.RemoveAll(path); err != nil {
-				// don't return error, because this path could have been removed already
-				logrus.Debugf("error removing %s from buildcontext", path)
+	for _, f := range files {
+		if rm, _ := fileutils.Matches(f, ignore); rm {
+			if err := os.RemoveAll(f); err != nil {
+				logrus.Errorf("Error removing %s from build context", f)
 			}
 		}
-		return nil
-	})
-}
-
-// ignoreFile returns true if the path matches any of the paths in ignore
-func ignoreFile(path string, ignore []string) bool {
-	for _, i := range ignore {
-		matched, err := filepath.Match(i, path)
-		if err != nil {
-			return false
-		}
-		if matched {
-			return true
-		}
 	}
-	return false
+	return nil
 }
 
 func exit(err error) {