Stylistic changes from cargo fmt and cargo clippy.

[jonathanKingston]

The clippy changes were:

warning: returning the result of a let binding from a block. Consider returning the expression directly.                                                                                                    
  --> src/lib.rs:38:5                                                                                                                                                                                       
   |                                                                                                                                                                                                        
38 |     context                                                                                                                                                                                            
   |     ^^^^^^^                                                                                                                                                                                            
   |                                                                                                                                                                                                        
   = note: #[warn(clippy::let_and_return)] on by default                                                                                                                                                    
note: this expression can be directly returned                                                                                                                                                              
  --> src/lib.rs:30:19                                                                                                                                                                                      
   |                                                                                                                                                                                                        
30 |       let context = match Context::from_host_config(host_config, opt) {                                                                                                                                
   |  ___________________^                                                                                                                                                                                  
31 | |         Ok(context) => context,                                                                                                                                                                      
32 | |         Err(message) => {                                                                                                                                                                            
33 | |             eprintln!("error: {:?}", message.description());                                                                                                                                         
34 | |             exit(1);                                                                                                                                                                                 
35 | |         }                                                                                                                                                                                            
36 | |     };                                                                                                                                                                                               
   | |_____^                                                                                                                                                                                                
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#let_and_return                                                                                 
                                                                                                                                                                                                            
warning: this argument is passed by value, but not consumed in the function body                                                                                                                            
  --> src/cmd.rs:45:20                                                                                                                                                                                      
   |                                                                                                                                                                                                        
45 |     resource_type: FSResourceType,                                                                                                                                                                     
   |                    ^^^^^^^^^^^^^^                                                                                                                                                                      
   |                                                                                                                                                                                                        
   = note: #[warn(clippy::needless_pass_by_value)] on by default                                                                                                                                            
help: consider marking this type as Copy                                                                                                                                                                    
  --> src/cmd.rs:9:1                                                                                                                                                                                        
   |                                                                                                                                                                                                        
9  | / pub enum FSResourceType {                                                                                                                                                                            
10 | |     File,                                                                                                                                                                                            
11 | |     Directory,                                                                                                                                                                                       
12 | |     Symlink,                                                                                                                                                                                         
13 | | }                                                                                                                                                                                                    
   | |_^                                                                                                                                                                                                    
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#needless_pass_by_value                                                                         
help: consider taking a reference instead                                                                                                                                                                   
   |                                                                                                                                                                                                        
45 |     resource_type: &FSResourceType,                                                                                                                                                                    
46 | ) -> Result<bool, io::Error> {                                                                                                                                                                         
47 |     let type_key = *match resource_type {                                                                                                                                                              
48 |         FSResourceType::File => "f",                                                                                                                                                                   
49 |         FSResourceType::Directory => "d",                                                                                                                                                              
50 |         FSResourceType::Symlink => "L",                                                                                                                                                                
 ...                                                                                                                                                                                                        
                                                                                                                                                                                                            
warning: this argument is passed by value, but not consumed in the function body                                                                                                                            
  --> src/cmd.rs:64:17                                                                                                                                                                                      
   |                                                                                                                                                                                                        
64 |     sort_order: SortOrder,                                                                                                                                                                             
   |                 ^^^^^^^^^                                                                                                                                                                              
   |                                                                                                                                                                                                        
help: consider marking this type as Copy                                                                                                                                                                    
  --> src/cmd.rs:15:1                                                                                                                                                                                       
   |                                                                                                                                                                                                        
15 | / pub enum SortOrder {                                                                                                                                                                                 
16 | |     Asc,                                                                                                                                                                                             
17 | |     Des,                                                                                                                                                                                             
18 | | }                                                                                                                                                                                                    
   | |_^                                                                                                                                                                                                    
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#needless_pass_by_value                                                                         
help: consider taking a reference instead                                                                                                                                                                   
   |                                                                                                                                                                                                        
64 |     sort_order: &SortOrder,                                                                                                                                                                            
65 | ) -> Result<Vec<String>, io::Error> {                                                                                                                                                                  
66 |     let sort_cmd = *match sort_order {                                                                                                                                                                 
67 |         SortOrder::Asc => "sort",                                                                                                                                                                      
68 |         SortOrder::Des => "sort -r",                                                                                                                                                                   
69 |     };                                                                                                                                                                                                 
 ...                                                                                                                                                                                                        
                                                                                                                                                                                                            
warning: redundant closure found                                                                                                                                                                            
  --> src/cmd.rs:81:14                                                                                                                                                                                      
   |                                                                                                                                                                                                        
81 |         .map(|x| String::from(x))                                                                                                                                                                      
   |              ^^^^^^^^^^^^^^^^^^^ help: remove closure as shown: `String::from`                                                                                                                         
   |                                                                                                                                                                                                        
   = note: #[warn(clippy::redundant_closure)] on by default                                                                                                                                                 
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#redundant_closure                                                                              
                                                                                                                                                                                                            
warning: single-character string constant used as pattern                                                                                                                                                   
  --> src/cmd.rs:80:16                                                                                                                                                                                      
   |                                                                                                                                                                                                        
80 |         .split("\n")                                                                                                                                                                                   
   |                ^^^^ help: try using a char instead: `'\n'`                                                                                                                                             
   |                                                                                                                                                                                                        
   = note: #[warn(clippy::single_char_pattern)] on by default                                                                                                                                               
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#single_char_pattern                                                                            
                                                                                                                                                                                                            
warning: use of `unwrap_or` followed by a call to `new`                                                                                                                                                     
  --> src/config/stages/mod.rs:57:21                                                                                                                                                                        
   |                                                                                                                                                                                                        
57 |         link_files: parse_string_vector("linked-files", &config_map).unwrap_or(Vec::new()),                                                                                                            
   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `parse_string_vector("linked-files", &config_map).unwrap_or_default()`                      
   |                                                                                                                                                                                                        
   = note: #[warn(clippy::or_fun_call)] on by default                                                                                                                                                       
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#or_fun_call                                                                                    
                                                                                                                                                                                                            
warning: use of `unwrap_or` followed by a call to `new`                                                                                                                                                     
  --> src/config/stages/mod.rs:58:20                                                                                                                                                                        
   |                                                                                                                                                                                                        
58 |         link_dirs: parse_string_vector("linked-dirs", &config_map).unwrap_or(Vec::new()),                                                                                                              
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `parse_string_vector("linked-dirs", &config_map).unwrap_or_default()`                         
   |                                                                                                                                                                                                        
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#or_fun_call                                                                                    
                                                                                                                                                                                                            
warning: use of `ok_or` followed by a function call                                                                                                                                                         
  --> src/config/steps/mod.rs:74:10                                                                                                                                                                         
   |                                                                                                                                                                                                        
74 |         .ok_or(BadType("name".into(), "string".into()))?                                                                                                                                               
   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `ok_or_else(|| BadType("name".into(), "string".into()))`                                                                       
   |                                                                                                                                                                                                        
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#or_fun_call                                                                                    
                                                                                                                                                                                                            
warning: use of `ok_or` followed by a function call                                                                                                                                                         
  --> src/config/steps/mod.rs:72:10                                                                                                                                                                         
   |                                                                                                                                                                                                        
72 |         .ok_or(MissingField("name".into()))?                                                                                                                                                           
   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `ok_or_else(|| MissingField("name".into()))`                                                                                               
   |                                                                                                                                                                                                        
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#or_fun_call                                                                                    
                                                                                                                                                                                                            
warning: use of `ok_or` followed by a function call                                                                                                                                                         
  --> src/config/steps/mod.rs:81:10                                                                                                                                                                         
   |                                                                                                                                                                                                        
81 |         .ok_or(BadType("command".into(), "string".into()))?                                                                                                                                            
   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `ok_or_else(|| BadType("command".into(), "string".into()))`                                                                 
   |                                                                                                                                                                                                        
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#or_fun_call                                                                                    
                                                                                                                                                                                                            
warning: use of `ok_or` followed by a function call                                                                                                                                                         
  --> src/config/steps/mod.rs:79:10                                                                                                                                                                         
   |                                                                                                                                                                                                        
79 |         .ok_or(MissingField("command".into()))?                                                                                                                                                        
   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `ok_or_else(|| MissingField("command".into()))`                                                                                         
   |                                                                                                                                                                                                        
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#or_fun_call                                                                                    
                                                                                                                                                                                                            
warning: use of `ok_or` followed by a function call                                                                                                                                                         
  --> src/config/steps/mod.rs:93:14                                                                                                                                                                         
   |                                                                                                                                                                                                        
93 |             .ok_or(BadType("before".into(), "string".into()))?                                                                                                                                         
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `ok_or_else(|| BadType("before".into(), "string".into()))`                                                               
   |                                                                                                                                                                                                        
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#or_fun_call                                                                                    
                                                                                                                                                                                                            
warning: use of `ok_or` followed by a function call                                                                                                                                                         
   --> src/config/steps/mod.rs:101:14                                                                                                                                                                       
    |                                                                                                                                                                                                       
101 |             .ok_or(BadType("after".into(), "string".into()))?                                                                                                                                         
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `ok_or_else(|| BadType("after".into(), "string".into()))`                                                                
    |                                                                                                                                                                                                       
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#or_fun_call                                                                                   
                                                                                                                                                                                                            
warning: writing `&Vec<_>` instead of `&[_]` involves one more reference and cannot be used with non-Vec-based slices.                                                                                      
  --> src/recipe/deployer.rs:32:25                                                                                                                                                                          
   |                                                                                                                                                                                                        
32 | fn execute_steps(steps: &Vec<Box<dyn Step>>, context: &Context) -> Result<(), String> {                                                                                                                
   |                         ^^^^^^^^^^^^^^^^^^^ help: change this to: `&[Box<dyn Step>]`                                                                                                                   
   |                                                                                                                                                                                                        
   = note: #[warn(clippy::ptr_arg)] on by default                                                                                                                                                           
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#ptr_arg                                                                                        
                                                                                                                                                                                                            
warning: useless use of `format!`                                                                                                                                                                           
  --> src/recipe/deployer.rs:44:35                                                                                                                                                                          
   |                                                                                                                                                                                                        
44 |                     render_error(&format!("Non-critical error, continuing"))                                                                                                                           
   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"Non-critical error, continuing".to_string()`                                          
   |                                                                                                                                                                                                        
   = note: #[warn(clippy::useless_format)] on by default                                                                                                                                                    
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#useless_format                                                                                 
                                                                                                                                                                                                            
warning: the variable `index` is used as a loop counter. Consider using `for (index, item) in &self.steps.enumerate()` or similar iterators                                                                 
  --> src/recipe/mod.rs:24:21                                                                                                                                                                               
   |                                                                                                                                                                                                        
24 |         for step in &self.steps {                                                                                                                                                                      
   |                     ^^^^^^^^^^^                                                                                                                                                                        
   |                                                                                                                                                                                                        
   = note: #[warn(clippy::explicit_counter_loop)] on by default                                                                                                                                             
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#explicit_counter_loop                                                                          
                                                                                                                                                                                                            
warning: use of `expect` followed by a function call                                                                                                                                                        
   --> src/recipe/mod.rs:103:22                                                                                                                                                                             
    |                                                                                                                                                                                                       
103 |                       .expect(&format!(                                                                                                                                                               
    |  ______________________^                                                                                                                                                                              
104 | |                         "Step '{}' doesn't exist in the recipe",                                                                                                                                    
105 | |                         &step_config.ref_step                                                                                                                                                       
106 | |                     ));                                                                                                                                                                             
    | |______________________^ help: try this: `unwrap_or_else(|| panic!("Step '{}' doesn't exist in the recipe", &step_config.ref_step))`                                                                  
    |                                                                                                                                                                                                       
    = note: #[warn(clippy::expect_fun_call)] on by default                                                                                                                                                  
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#expect_fun_call                                                                               
                                                                                                                                                                                                            
warning: use of `expect` followed by a function call                                                                                                                                                        
   --> src/recipe/mod.rs:132:18                                                                                                                                                                             
    |                                                                                                                                                                                                       
132 |                   .expect(&format!(                                                                                                                                                                   
    |  __________________^                                                                                                                                                                                  
133 | |                     "Step '{}' doesn't exist in the recipe",                                                                                                                                        
134 | |                     subject_name                                                                                                                                                                    
135 | |                 ));                                                                                                                                                                                 
    | |__________________^ help: try this: `unwrap_or_else(|| panic!("Step '{}' doesn't exist in the recipe", subject_name))`                                                                               
    |                                                                                                                                                                                                       
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#expect_fun_call                                                                               
                                                                                                                                                                                                            
warning: use of `expect` followed by a function call                                                                                                                                                        
   --> src/recipe/mod.rs:158:18                                                                                                                                                                             
    |                                                                                                                                                                                                       
158 |                   .expect(&format!(                                                                                                                                                                   
    |  __________________^                                                                                                                                                                                  
159 | |                     "Step '{}' doesn't exist in the recipe",                                                                                                                                        
160 | |                     subject_name                                                                                                                                                                    
161 | |                 ));                                                                                                                                                                                 
    | |__________________^ help: try this: `unwrap_or_else(|| panic!("Step '{}' doesn't exist in the recipe", subject_name))`                                                                               
    |                                                                                                                                                                                                       
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#expect_fun_call                                                                               
                                                                                                                                                                                                            
warning: redundant closure found                                                                                                                                                                            
   --> src/steps/core.rs:218:19                                                                                                                                                                             
    |                                                                                                                                                                                                       
218 |         ).map_err(|e| StepError::non_critical_from_error(e))?;                                                                                                                                        
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove closure as shown: `StepError::non_critical_from_error`                                                                       
    |                                                                                                                                                                                                       
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#redundant_closure                                                                             
                                                                                                                                                                                                            
warning: this argument is passed by value, but not consumed in the function body                                                                                                                            
  --> src/steps/error.rs:25:53                                                                                                                                                                              
   |                                                                                                                                                                                                        
25 |     pub fn non_critical_from_error<E: Error>(error: E) -> Self {                                                                                                                                       
   |                                                     ^ help: consider taking a reference instead: `&E`                                                                                                  
   |                                                                                                                                                                                                        
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#needless_pass_by_value                                                                         
                                                                                                                                                                                                            
warning: use of `ok_or` followed by a function call                                                                                                                                                         
  --> src/steps/rollback.rs:17:14                                                                                                                                                                           
   |                                                                                                                                                                                                        
17 |             .ok_or(StepError::Critical(NO_PREV_ERR_MSG.into()))                                                                                                                                        
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `ok_or_else(|| StepError::Critical(NO_PREV_ERR_MSG.into()))`                                                           
   |                                                                                                                                                                                                        
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#or_fun_call                                                                                    
                                                                                                                                                                                                            
warning: you seem to be trying to match on a boolean expression                                                                                                                                             
  --> src/steps/rollback.rs:38:9                                                                                                                                                                            
   |                                                                                                                                                                                                        
38 | /         match output.status.success() {                                                                                                                                                              
39 | |             true => Ok(()),                                                                                                                                                                          
40 | |             false => {                                                                                                                                                                               
41 | |                 let err_msg = format!("Failed to remove current release at {}", release_path);                                                                                                       
42 | |                 Err(StepError::Critical(err_msg))                                                                                                                                                    
43 | |             }                                                                                                                                                                                        
44 | |         }                                                                                                                                                                                            
   | |_________^                                                                                                                                                                                            
   |                                                                                                                                                                                                        
   = note: #[warn(clippy::match_bool)] on by default                                                                                                                                                        
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#match_bool                                                                                     
help: consider using an if/else expression                                                                                                                                                                  
   |                                                                                                                                                                                                        
38 |         if output.status.success() { Ok(()) } else {                                                                                                                                                   
39 |     let err_msg = format!("Failed to remove current release at {}", release_path);                                                                                                                     
40 |     Err(StepError::Critical(err_msg))                                                                                                                                                                  
41 | }                                                                                                                                                                                                      
   |                                                                                                                                                                                                        
                                                                                                                                                                                                            
warning: this argument is passed by value, but not consumed in the function body                                                                                                                            
  --> src/steps/mod.rs:22:54                                                                                                                                                                                
   |                                                                                                                                                                                                        
22 |     pub fn from_host_config(config: HostConfig, opt: Operation) -> Result<Context, Error> {                                                                                                            
   |                                                      ^^^^^^^^^                                                                                                                                         
   |                                                                                                                                                                                                        
help: consider marking this type as Copy                                                                                                                                                                    
  --> src/lib.rs:16:1                                                                                                                                                                                       
   |                                                                                                                                                                                                        
16 | / pub enum Operation {                                                                                                                                                                                 
17 | |     Deploy,                                                                                                                                                                                          
18 | |     Rollback,                                                                                                                                                                                        
19 | | }                                                                                                                                                                                                    
   | |_^                                                                                                                                                                                                    
   = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#needless_pass_by_value                                                                         
help: consider taking a reference instead                                                                                                                                                                   
   |                                                                                                                                                                                                        
22 |     pub fn from_host_config(config: HostConfig, opt: &Operation) -> Result<Context, Error> {                                                                                                           
23 |         match *opt {                                                                                                                                                                                   
   |                                                                                                                                                                                                        
                                                                                                                                                                                                            
warning: Constants have by default a `'static` lifetime                                                                                                                                                     
 --> src/main.rs:9:15                                                                                                                                                                                       
  |                                                                                                                                                                                                         
9 | const USAGE: &'static str = "                                                                                                                                                                           
  |              -^^^^^^^---- help: consider removing `'static`: `&str`                                                                                                                                     
  |                                                                                                                                                                                                         
  = note: #[warn(clippy::const_static_lifetime)] on by default                                                                                                                                              
  = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#const_static_lifetime                                      

Looks like the code will work in the 2018 edition too cargo fix makes no changes.