history: add export command

Allow builds to be exported into .dockerbuild bundles
that can be shared and imported into Docker Desktop.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

commands/history/root.go

@@ -26,6 +26,7 @@ func RootCmd(rootcmd *cobra.Command, dockerCli command.Cli, opts RootOptions) *c
 		openCmd(dockerCli, opts),
 		traceCmd(dockerCli, opts),
 		importCmd(dockerCli, opts),
+		exportCmd(dockerCli, opts),
 	)
 
 	return cmd