mix: add Nerves tasks to completion (#7180)

plugins/mix/README.md

@@ -16,3 +16,4 @@ plugins=(... mix)
 | Phoenix v1.3.0 and above| [Phoenix](https://hexdocs.pm/phoenix/Phoenix.html)       |
 | Ecto                    | [Ecto](https://hexdocs.pm/ecto/Ecto.html)                |
 | Hex                     | [Hex](https://hex.pm/)                                   |
+| Nerves                  | [Nerves](https://nerves-project.org/)                    |

plugins/mix/_mix

@@ -31,6 +31,9 @@ _1st_arguments=(
     'ecto.migrations:Displays the up / down migration status'
     'ecto.rollback:Reverts applied migrations'
     'escript.build:Builds an escript for the project'
+    'firmware:Nerves - Build a firmware image for the selected target platform'
+    'firmware.burn:Nerves - Writes the generated firmware image to an attached SDCard or file'
+    'firmware.image:Nerves - Create a firmware image file that can be copied byte-for-byte'
     'help:Print help information for tasks'
     'hex:Print hex help information'
     'hex.config:Read or update hex config'
@@ -48,6 +51,11 @@ _1st_arguments=(
     'local.phoenix:Updates Phoenix locally'
     'local.phx:Updates the Phoenix project generator locally'
     'local.rebar:Install rebar locally'
+    'nerves.artifact:Create an artifact for a specified Nerves package'
+    'nerves.artifact.get:Nerves get artifacts'
+    'nerves.info:Prints Nerves system information'
+    'nerves.new:Create a new Nerves application'
+    'nerves.release.init:Prepare a new Nerves project for use with releases'
     'new:Create a new Elixir project'
     'phoenix.digest:Digests and compress static files'
     'phoenix.gen.channel:Generates a Phoenix channel'