allow passing emoji for avatar icon

.env.dist

@@ -5,6 +5,7 @@
 SLACK_WEBHOOK=
 SLACK_CHANNEL=
 SLACK_AVATAR=sender
+SLACK_EMOJI=
 SLACK_USERNAME=$USER
 # SLACK_CUSTOM_PAYLOAD=
 

README.md

@@ -25,6 +25,7 @@ This GitHub action is part of a list of Actions that are located in an other rep
     SLACK_USERNAME: ThisIsMyUsername # Optional. (defaults to webhook app)
     SLACK_CHANNEL: general # Optional. (defaults to webhook)
     SLACK_AVATAR: repository # Optional. can be (repository, sender, an URL) (defaults to webhook app avatar)
+    SLACK_EMOJI: octocat # Optional. (defaults to null)
   uses: Ilshidur/action-slack@2.0.2
   with:
     args: 'A new commit has been pushed.' # Optional
@@ -62,6 +63,7 @@ e.g.: `Action called: {{ GITHUB_ACTION }} as {{ EVENT_PAYLOAD.pull_request.id }}
 * **`SLACK_USERNAME`** *(optional)* : overrides username. Defaults to the Slack webhook bot name.
 * **`SLACK_CHANNEL`** *(optional)* : overrides the default channel of the webhook. If not set, the message will be sent to the channel associated to the webhook.
 * **`SLACK_AVATAR`** *(optional)* : overrides the message avatar. Can be `'repository'`, `'sender'` or an URL. If not set, the avatar of the Slack webhook's bot picture will be used.
+* **`SLACK_EMOJI`** *(optional)* : overrides the message avatar. If not set, the avatar of the Slack webhook's bot picture will be used.
 * **`SLACK_CUSTOM_PAYLOAD`** *(advanced)* : JSON string that sets full payload. instructions see [CUSTOM_PAYLOAD](CUSTOM_PAYLOAD.md)
 
 ## Debugging / testing / development

handlers.js

@@ -6,6 +6,7 @@ _.templateSettings.interpolate = /{{([\s\S]+?)}}/g;
 
 const {
   SLACK_AVATAR,
+  SLACK_EMOJI,
   SLACK_CUSTOM_PAYLOAD,
   GITHUB_EVENT_PATH,
   GITHUB_ACTOR,
@@ -40,3 +41,7 @@ exports.selectAvatar = () => {
     default: return SLACK_AVATAR || false;
   }
 };
+
+exports.emoji = () => {
+  return SLACK_EMOJI ? `:${SLACK_EMOJI}:` : null
+};

message.js

@@ -2,7 +2,7 @@
   @description
   Message payload to be sent with Slack webhook
 */
-const { selectAvatar, getMessage, parsePayload } = require("./handlers");
+const { selectAvatar, emoji, getMessage, parsePayload } = require("./handlers");
 
 const {
   SLACK_USERNAME,
@@ -33,6 +33,12 @@ const messageSingleton = (() => {
     */
     if (selectAvatar()) message.icon_url = selectAvatar();
 
+    /*
+      If provided emoji add it,
+      defaults to null;
+    */
+    if (emoji()) message.icon_emoji = emoji();
+
     return message;
   }