feat: add optional yarn_install_directory parameter (#124)

* yarn_install - add optional yarn_install_directory parameter

* Fix spelling and add default

* Only use --cwd if yarn_install_directory is not empty string

Author: joshdholtz

src/commands/yarn_install.yml

@@ -9,6 +9,10 @@ parameters:
     description: The path to the yarn cache folder.  Defaults to /tmp/yarn
     type: string
     default: "/tmp/yarn"
+  yarn_install_directory:
+    description: The working directory to run install at. Defaults to yarn's current working directory
+    type: string
+    default: ""
 
 steps:
   - when:
@@ -23,9 +27,20 @@ steps:
         - restore_cache:
             keys:
               - yarn-cache-{{ arch }}-{{ checksum "~/.tmp/checksumfiles/package.json" }}-{{ checksum "~/.tmp/checksumfiles/yarn.lock" }}-{{ .Environment.CACHE_VERSION }}
-  - run:
-      name: Yarn Install
-      command: "yarn install --frozen-lockfile --non-interactive --cache-folder <<parameters.cache_folder>>"
+  - when:
+      condition:
+        equal: ["", <<parameters.yarn_install_directory>>]
+      steps:
+        - run:
+            name: Yarn Install
+            command: "yarn install --frozen-lockfile --non-interactive --cache-folder <<parameters.cache_folder>>"
+  - unless:
+      condition:
+        equal: ["", <<parameters.yarn_install_directory>>]
+      steps:
+        - run:
+            name: Yarn Install (<<parameters.yarn_install_directory>>)
+            command: "yarn --cwd <<parameters.yarn_install_directory>> install --frozen-lockfile --non-interactive --cache-folder <<parameters.cache_folder>>"
   - when:
       condition: <<parameters.cache>>
       steps: