Add clearer placeholders and channel definition.

app/models/project_services/mattermost_service.rb

@@ -15,10 +15,10 @@ class MattermostService < ChatNotificationService
     'This service sends notifications about projects events to Mattermost channels.<br />
     To set up this service:
     <ol>
-      <li><a href="https://docs.mattermost.com/developer/webhooks-incoming.html#enabling-incoming-webhooks">Enable incoming webhooks</a> in your Mattermost installation. </li>
-      <li><a href="https://docs.mattermost.com/developer/webhooks-incoming.html#creating-integrations-using-incoming-webhooks">Add an incoming webhook</a> in your Mattermost team. The default channel can be overridden for each event. </li>
-      <li>Paste the webhook <strong>URL</strong> into the field bellow. </li>
-      <li>Select events below to enable notifications. The channel and username are optional. </li>
+      <li><a href="https://docs.mattermost.com/developer/webhooks-incoming.html#enabling-incoming-webhooks">Enable incoming webhooks</a> in your Mattermost installation.</li>
+      <li><a href="https://docs.mattermost.com/developer/webhooks-incoming.html#creating-integrations-using-incoming-webhooks">Add an incoming webhook</a> in your Mattermost team. The default channel can be overridden for each event.</li>
+      <li>Paste the webhook <strong>URL</strong> into the field below.</li>
+      <li>Select events below to enable notifications. The <strong>Channel handle</strong> and <strong>Username</strong> fields are optional.</li>
     </ol>'
   end
 
@@ -28,14 +28,14 @@ class MattermostService < ChatNotificationService
 
   def default_fields
     [
-      { type: 'text', name: 'webhook', placeholder: 'http://mattermost_host/hooks/...' },
-      { type: 'text', name: 'username', placeholder: 'username' },
+      { type: 'text', name: 'webhook', placeholder: 'e.g. http://mattermost_host/hooks/…' },
+      { type: 'text', name: 'username', placeholder: 'e.g. GitLab' },
       { type: 'checkbox', name: 'notify_only_broken_builds' },
       { type: 'checkbox', name: 'notify_only_broken_pipelines' },
     ]
   end
 
   def default_channel_placeholder
-    "town-square"
+    "Channel handle (e.g. town-square)"
   end
 end

app/models/project_services/slack_service.rb

@@ -13,11 +13,11 @@ class SlackService < ChatNotificationService
 
   def help
     'This service sends notifications about projects events to Slack channels.<br />
-    To setup this service:
+    To set up this service:
     <ol>
-      <li><a href="https://slack.com/apps/A0F7XDUAZ-incoming-webhooks">Add an incoming webhook</a> in your Slack team. The default channel can be overridden for each event. </li>
-      <li>Paste the <strong>Webhook URL</strong> into the field below. </li>
-      <li>Select events below to enable notifications. The channel and username are optional. </li>
+      <li><a href="https://slack.com/apps/A0F7XDUAZ-incoming-webhooks">Add an incoming webhook</a> in your Slack team. The default channel can be overridden for each event.</li>
+      <li>Paste the <strong>Webhook URL</strong> into the field below.</li>
+      <li>Select events below to enable notifications. The <strong>Channel name</strong> and <strong>Username</strong> fields are optional.</li>
     </ol>'
   end
 
@@ -27,14 +27,14 @@ class SlackService < ChatNotificationService
 
   def default_fields
     [
-      { type: 'text', name: 'webhook', placeholder: 'https://hooks.slack.com/services/...' },
-      { type: 'text', name: 'username', placeholder: 'username' },
+      { type: 'text', name: 'webhook', placeholder: 'e.g. https://hooks.slack.com/services/…' },
+      { type: 'text', name: 'username', placeholder: 'e.g. GitLab' },
       { type: 'checkbox', name: 'notify_only_broken_builds' },
       { type: 'checkbox', name: 'notify_only_broken_pipelines' },
     ]
   end
 
   def default_channel_placeholder
-    "#general"
+    "Channel name (e.g. general)"
   end
 end