Replace gometalinter with GolangCI-Lint

gometalinter is broken @ HEAD, and I looked into why that was. During
that process, I remembered that we took the linting scripts from
skaffold, and found that in skaffold gometalinter was replaced with
GolangCI-Lint:

GoogleContainerTools/skaffold#619

The change made linting in skaffold faster, so I figured instead of
fixing gometalinter it made more sense to remove it and replace it with
GolangCI-Lint for kaniko as well.

cmd/executor/cmd/root.go

@@ -86,7 +86,7 @@ func addKanikoOptionsFlags(cmd *cobra.Command) {
 	RootCmd.PersistentFlags().StringVarP(&opts.SnapshotMode, "snapshotMode", "", "full", "Change the file attributes inspected during snapshotting")
 	RootCmd.PersistentFlags().VarP(&opts.BuildArgs, "build-arg", "", "This flag allows you to pass in ARG values at build time. Set it repeatedly for multiple values.")
 	RootCmd.PersistentFlags().BoolVarP(&opts.InsecurePush, "insecure", "", false, "Push to insecure registry using plain HTTP")
-	RootCmd.PersistentFlags().BoolVarP(&opts.SkipTlsVerify, "skip-tls-verify", "", false, "Push to insecure registry ignoring TLS verify")
+	RootCmd.PersistentFlags().BoolVarP(&opts.SkipTLSVerify, "skip-tls-verify", "", false, "Push to insecure registry ignoring TLS verify")
 	RootCmd.PersistentFlags().StringVarP(&opts.TarPath, "tarPath", "", "", "Path to save the image in as a tarball instead of pushing")
 	RootCmd.PersistentFlags().BoolVarP(&opts.SingleSnapshot, "single-snapshot", "", false, "Take a single snapshot at the end of the build.")
 	RootCmd.PersistentFlags().BoolVarP(&opts.Reproducible, "reproducible", "", false, "Strip timestamps out of the image to make it reproducible")
@@ -145,7 +145,7 @@ func resolveSourceContext() error {
 			opts.SrcContext = opts.Bucket
 		}
 	}
-	// if no prefix use Google Cloud Storage as default for backwards compability
+	// if no prefix use Google Cloud Storage as default for backwards compatibility
 	contextExecutor, err := buildcontext.GetBuildContext(opts.SrcContext)
 	if err != nil {
 		return err

hack/boilerplate/boilerplate.py

@@ -18,12 +18,14 @@
 
 import argparse
 import glob
-import json
-import mmap
 import os
 import re
 import sys
 
+
+SKIPPED_DIRS = ["Godeps", "third_party", ".git", "vendor", "examples", "testdata"]
+SKIPPED_FILES = ["install_golint.sh"]
+
 parser = argparse.ArgumentParser()
 parser.add_argument("filenames", help="list of files to check, all files if unspecified", nargs='*')
 
@@ -71,7 +73,7 @@ def file_passes(filename, refs, regexs):
         (data, found) = p.subn("", data, 1)
 
     # remove shebang from the top of shell files
-    if extension == "sh":
+    elif extension == "sh":
         p = regexs["shebang"]
         (data, found) = p.subn("", data, 1)
 
@@ -105,17 +107,11 @@ def file_passes(filename, refs, regexs):
 def file_extension(filename):
     return os.path.splitext(filename)[1].split(".")[-1].lower()
 
-skipped_dirs = ['Godeps', 'third_party', '.git', "vendor", "differs/testDirs/pipTests"]
-
 def normalize_files(files):
     newfiles = []
-    for pathname in files:
-        if any(x in pathname for x in skipped_dirs):
-            continue
-        newfiles.append(pathname)
-    for i, pathname in enumerate(newfiles):
+    for i, pathname in enumerate(files):
         if not os.path.isabs(pathname):
-            newfiles[i] = os.path.join(args.rootdir, pathname)
+            newfiles.append(os.path.join(args.rootdir, pathname))
     return newfiles
 
 def get_files(extensions):
@@ -124,17 +120,14 @@ def get_files(extensions):
         files = args.filenames
     else:
         for root, dirs, walkfiles in os.walk(args.rootdir):
-            # don't visit certain dirs. This is just a performance improvement
-            # as we would prune these later in normalize_files(). But doing it
-            # cuts down the amount of filesystem walking we do and cuts down
-            # the size of the file list
-            for d in skipped_dirs:
+            for d in SKIPPED_DIRS:
                 if d in dirs:
                     dirs.remove(d)
 
             for name in walkfiles:
-                pathname = os.path.join(root, name)
-                files.append(pathname)
+                if name not in SKIPPED_FILES:
+                    pathname = os.path.join(root, name)
+                    files.append(pathname)
 
     files = normalize_files(files)
     outfiles = []