Implement env add command

lib/actions/environment-variables.coffee

@@ -24,3 +24,18 @@ exports.remove = permissions.user (params, options) ->
 	ui.patterns.remove 'environment variable', options.yes, (callback) ->
 		resin.models.environmentVariables.remove(params.id, callback)
 	, resin.errors.handle
+
+exports.add = permissions.user (params, options) ->
+	if not options.application?
+		resin.errors.handle(new Error('You have to specify an application'))
+
+	if not params.value?
+		params.value = process.env[params.key]
+
+		if not params.value?
+			resin.errors.handle(new Error("Environment value not found for key: #{params.key}"))
+		else
+			resin.log.info("Warning: using #{params.key}=#{params.value} from host environment")
+
+	resin.models.environmentVariables.create options.application, params.key, params.value, (error) ->
+		resin.errors.handle(error) if error?

lib/app.coffee

@@ -37,6 +37,12 @@ yesOption =
 	boolean: true
 	alias: 'y'
 
+applicationOption =
+	signature: 'application'
+	parameter: 'application'
+	description: 'application id'
+	alias: [ 'a', 'app' ]
+
 # ---------- Auth Module ----------
 capitano.command
 	signature: 'login [credentials]'
@@ -326,12 +332,8 @@ capitano.command
 	'''
 	action: actions.env.list
 	options: [
-		{
-			signature: 'application'
-			parameter: 'application'
-			description: 'application id'
-			alias: [ 'a', 'app' ]
-		}
+		applicationOption
+
 		{
 			signature: 'verbose'
 			description: 'show private environment variables'
@@ -340,6 +342,27 @@ capitano.command
 		}
 	]
 
+capitano.command
+	signature: 'env add <key> [value]'
+	description: 'add an environment variable'
+	help: '''
+		Use this command to add an enviroment variable to an application.
+
+		You need to pass the `--application` option.
+
+		If value is omitted, the tool will attempt to use the variable's value
+		as defined in your host machine.
+
+		If the value is grabbed from the environment, a warning message will be printed.
+		Use `--quiet` to remove it.
+
+		Examples:
+			$ resin env add EDITOR vim -a 91
+			$ resin env add TERM -a 91
+	'''
+	options: [ applicationOption ]
+	action: actions.env.add
+
 capitano.command
 	signature: 'env rm <id>'
 	description: 'remove an environment variable'

lib/resin/models/environment-variables.coffee

@@ -30,6 +30,31 @@ exports.getAllByApplication = (applicationId, callback) ->
 	.catch (error) ->
 		return callback(error)
 
+# Create an environment variable for an application
+#
+# @param {String, Number} applicationId application id
+# @param {String} name environment variable name
+# @param {String} value environment variable value
+# @param {Function} callback callback(error)
+#
+# @example Create an environment variable
+#		resin.models.environmentVariables.create 91, 'EDITOR', 'vim', (error) ->
+#			throw error if error?
+#
+exports.create = (applicationId, name, value, callback) ->
+	return pine.post
+		resource: 'environment_variable'
+		data:
+			name: name
+			value: value
+			application: applicationId
+
+	.then ->
+		return callback()
+
+	.catch (error) ->
+		return callback(error)
+
 # Remove environment variable
 #
 # @param {String, Number} id environment variable id