Pass CommandEnv struct to command exec function

So we can add parameters rather easily.
Also define CommandResult as result type.

src/module/bm/commands.rs

@@ -1,15 +1,18 @@
 use runtime::Runtime;
 use storage::backend::StorageBackend;
 
-pub fn add_command(rt: &Runtime, backend: &StorageBackend) {
+use module::CommandResult;
+use module::CommandEnv;
+
+pub fn add_command(env: CommandEnv) -> CommandResult {
     unimplemented!()
 }
 
-pub fn list_command(rt: &Runtime, backend: &StorageBackend) {
+pub fn list_command(env: CommandEnv) -> CommandResult {
     unimplemented!()
 }
 
-pub fn remove_command(rt: &Runtime, backend: &StorageBackend) {
+pub fn remove_command(env: CommandEnv) -> CommandResult {
     unimplemented!()
 }
 

src/module/mod.rs

@@ -6,6 +6,8 @@ use std::fmt::Display;
 use std::result::Result;
 use std::collections::HashMap;
 
+use clap::{App, ArgMatches};
+
 use storage::backend::{StorageBackend, StorageBackendError};
 
 pub mod bm;
@@ -41,8 +43,15 @@ impl Display for ModuleError {
     }
 }
 
+pub struct CommandEnv<'a> {
+    pub rt:         &'a Runtime<'a>,
+    pub bk:         &'a StorageBackend,
+    pub matches:    &'a ArgMatches<'a, 'a>,
+}
+
 pub type ModuleResult = Result<(), ModuleError>;
-pub type CommandMap<'a> = HashMap<&'a str, fn(&Runtime, &StorageBackend)>;
+pub type CommandResult  = ModuleResult;
+pub type CommandMap<'a> = HashMap<&'a str, fn(CommandEnv) -> CommandResult>;
 
 pub trait Module {