Update master

Author: Travis CI dpl test (via Travis CI)

user/billing-faq.md

@@ -90,3 +90,9 @@ To help you track the build credit consumption Travis CI system will send the no
 ## Are add-ons limited to a certain number of users?
 
 You can buy additional add-ons any time you feel it is needed. You and your organization’s members can use the bought add-ons with no limitations.
+
+## Why my credits balance is negative?
+
+Most probably your last build costed more than you had available in your credit balance. You won't be able to run any builds until your balance gets positive. Replenish your credits (the negative balance will be deducted upon arrival of new credits creating new balance - see our [billing overview](/user/billing-overview/#negative-credits).
+
+

user/billing-overview.md

@@ -101,6 +101,10 @@ You may disband your credits. It will happen when
 
 and is meant to prevent abusive usage of the system.
 
+#### Negative Credits
+
+By design, the billing system allows the build job to be finished even if the possible cost of build job expressed in credits exceeds available credits balance. After such build being finished you may notice your credit balance being negative. **This is perfectly normal.** Whenever your credits get replenished, e.g. after purchasing an addon, the negative balance will be deducted from newly arriving credit pool. What remains is your available credits balance for your builds.
+
 
 #### Credits vs. OSS Only Credits
 

user/deployment/pages.md

@@ -23,7 +23,7 @@ deploy:
   github_token: $GITHUB_TOKEN  # Set in the settings page of your repository, as a secure variable
   keep_history: true
   on:
-    branch: master
+    branch: main
 ```
 {: data-file=".travis.yml"}