Fix positional args, tweak err handling for promote/demote/delete

Signed-off-by: Salim Alam <salam@chef.io>

components/hab/src/cli.rs

@@ -546,8 +546,8 @@ pub fn get() -> App<'static, 'static> {
                     environment variable if defined. (default: https://bldr.habitat.sh)")
                 (@arg PKG_IDENT: +required +takes_value {valid_fully_qualified_ident} "A fully qualified package identifier \
                     (ex: core/busybox-static/1.42.2/20170513215502)")
-                (arg: arg_target())
                 (@arg CHANNEL: +required +takes_value "Promote to the specified release channel")
+                (arg: arg_target())
                 (@arg AUTH_TOKEN: -z --auth +takes_value "Authentication token for Builder")
             )
             (@subcommand demote =>
@@ -558,8 +558,8 @@ pub fn get() -> App<'static, 'static> {
                     environment variable if defined. (default: https://bldr.habitat.sh)")
                 (@arg PKG_IDENT: +required +takes_value {valid_fully_qualified_ident} "A fully qualified package identifier \
                     (ex: core/busybox-static/1.42.2/20170513215502)")
-                (arg: arg_target())
                 (@arg CHANNEL: +required +takes_value "Demote from the specified release channel")
+                (arg: arg_target())
                 (@arg AUTH_TOKEN: -z --auth +takes_value "Authentication token for Builder")
             )
             (@subcommand channels =>

components/hab/src/command/pkg/delete.rs

@@ -12,7 +12,8 @@
 //!
 //! //! Note: This command does not remove the package from disk
 
-use crate::{api_client::Client,
+use crate::{api_client::{self,
+                         Client},
             common::ui::{Status,
                          UIWriter,
                          UI},
@@ -22,6 +23,7 @@ use crate::{api_client::Client,
                              PackageTarget},
             PRODUCT,
             VERSION};
+use hyper::status::StatusCode;
 
 /// Delete a package from Builder.
 ///
@@ -39,6 +41,9 @@ pub fn start(ui: &mut UI,
 
     if let Err(err) = api_client.delete_package((ident, target), token) {
         println!("Failed to delete '{}': {:?}", ident, err);
+        if let api_client::Error::APIError(StatusCode::NotFound, _) = err {
+            println!("Perhaps you may need to specify a platform target argument");
+        }
         return Err(Error::from(err));
     }
 

components/hab/src/command/pkg/demote.rs

@@ -25,13 +25,15 @@
 //!    The package should already have been uploaded to Builder.
 //!    If the specified channel does not exist, this will fail.
 
-use crate::{api_client::Client,
+use crate::{api_client::{self,
+                         Client},
             common::ui::{Status,
                          UIWriter,
                          UI},
             hcore::{package::{PackageIdent,
                               PackageTarget},
                     ChannelIdent}};
+use hyper::status::StatusCode;
 
 use crate::{error::{Error,
                     Result},
@@ -63,6 +65,9 @@ pub fn start(ui: &mut UI,
         Ok(_) => (),
         Err(e) => {
             println!("Failed to demote '{}': {:?}", ident, e);
+            if let api_client::Error::APIError(StatusCode::NotFound, _) = e {
+                println!("Perhaps you may need to specify a platform target argument");
+            }
             return Err(Error::from(e));
         }
     }

components/hab/src/command/pkg/promote.rs

@@ -70,6 +70,9 @@ pub fn start(ui: &mut UI,
         Ok(_) => (),
         Err(e) => {
             println!("Failed to promote '{}': {:?}", ident, e);
+            if let api_client::Error::APIError(StatusCode::NotFound, _) = e {
+                println!("Perhaps you may need to specify a platform target argument");
+            }
             return Err(Error::from(e));
         }
     }