Support for Compressed, Base64-Enc, Inline Content

This patch adds support for local, inline content as compressed, base64
encoded values. For example, the string "Hello, world." can be
compressed with gzip and base64 encoded with the following command:

        $ echo Hello, world. | gzip | base64
        H4sIAG/kFlsAA/NIzcnJ11Eozy/KSdHjAgDXu838DgAAAA==

A Container Linux Config could use the above contents and write them to
the file "/etc/helloworld.txt":

        storage:
            files:
            - path: /etc/helloworld.txt
                filesystem: root
                mode: 0644
                contents:
                compression: gzip
                inline: !binary |
                    H4sIAB/jFlsAA/NIzcnJ11Eozy/KSdHjAgDXu838DgAAAA==

The CT transpiler would transform the above configuration snippet into
the JSON below:

        {
            "filesystem": "root",
            "path": "/etc/helloworld.txt",
            "contents": {
                "compression": "gzip",
                "source": "data:,H4sIAB%2FjFlsAA%2FNIzcnJ11Eozy%2FKSdHjAgDXu838DgAAAA%3D%3D",
                "verification": {}
            },
            "mode": 420
        },

The following command may be used to verify the URL encoded data matches the
original "Hello, world." string:

        $ echo H4sIAB%2FjFlsAA%2FNIzcnJ11Eozy%2FKSdHjAgDXu838DgAAAA%3D%3D | \
          perl -pe 's/\%(\w\w)/chr hex $1/ge' | \
          base64 -D | \
          gzip -d
        Hello, world.

Author: akutz

config/types/files.go

@@ -63,14 +63,14 @@ type File struct {
 }
 
 type FileContents struct {
-	Remote Remote `yaml:"remote"`
-	Inline string `yaml:"inline"`
-	Local  string `yaml:"local"`
+	Compression string `yaml:"compression"`
+	Remote      Remote `yaml:"remote"`
+	Inline      string `yaml:"inline"`
+	Local       string `yaml:"local"`
 }
 
 type Remote struct {
 	Url          string       `yaml:"url"`
-	Compression  string       `yaml:"compression"`
 	Verification Verification `yaml:"verification"`
 }
 
@@ -237,7 +237,7 @@ func init() {
 				}
 			}
 
-			newFile.Contents.Compression = file.Contents.Remote.Compression
+			newFile.Contents.Compression = file.Contents.Compression
 			newFile.Contents.Verification = convertVerification(file.Contents.Remote.Verification)
 
 			out.Storage.Files = append(out.Storage.Files, newFile)

doc/configuration.md

@@ -63,10 +63,10 @@ _Note: all fields are optional unless otherwise marked_
     * **overwrite** (boolean): whether to delete preexisting nodes at the path. Defaults to true.
     * **append** (boolean): whether to append to the specified file. Creates a new file if nothing exists at the path. Cannot be set if overwrite is set to true.
     * **contents** (object): options related to the contents of the file.
+      * **compression** (string): the type of compression used on the contents (null or gzip)
       * **inline** (string): the contents of the file.
       * **local** (string): the path to a local file, relative to the `--files-dir` directory. When using local files, the `--files-dir` flag must be passed to `ct`. The file contents are included in the generated config.
       * **remote** (object): options related to the fetching of remote file contents. Remote files are fetched by Ignition when Ignition runs, the contents are not included in the generated config.
-        * **compression** (string): the type of compression used on the contents (null or gzip)
         * **url** (string): the URL of the file contents. Supported schemes are http, https, tftp, s3, and [data][rfc2397]. Note: When using http, it is advisable to use the verification option to ensure the contents haven't been modified.
         * **verification** (object): options related to the verification of the file contents.
           * **hash** (object): the hash of the config