Remove last traces of Travis CI

* The build status badge is now for GitHub Actions.
* The documentation now mentions GitHub instead.
* Warnings in the YAML file have been fixed or ignored.

.github/workflows/main.yml

@@ -1,11 +1,12 @@
+---
 name: CI
-on:
+on:  # yamllint disable-line rule:truthy
   push:
-    branches: [ master ]
+    branches: [ master ]  # yamllint disable-line rule:brackets
     tags:
       - /^v\d+\.\d+\.(x|\d+)$/
   pull_request:
-    branches: [ master ]
+    branches: [ master ]  # yamllint disable-line rule:brackets
 
 jobs:
   build_image:

README.md

@@ -1,4 +1,4 @@
-# Asynchronous Lint Engine [![Travis CI Build Status](https://travis-ci.com/dense-analysis/ale.svg?branch=master)](https://travis-ci.com/dense-analysis/ale) [![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/r0ef1xu8xjmik58d/branch/master?svg=true)](https://ci.appveyor.com/project/dense-analysis/ale) [![Join the chat at https://gitter.im/vim-ale/Lobby](https://badges.gitter.im/vim-ale/Lobby.svg)](https://gitter.im/vim-ale/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+# Asynchronous Lint Engine [![GitHub Build Status](https://github.com/dense-analysis/ale/workflows/CI/badge.svg)](https://github.com/dense-analysis/ale/actions?query=event%3Apush+workflow%3ACI+branch%3Amaster++) [![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/r0ef1xu8xjmik58d/branch/master?svg=true)](https://ci.appveyor.com/project/dense-analysis/ale) [![Join the chat at https://gitter.im/vim-ale/Lobby](https://badges.gitter.im/vim-ale/Lobby.svg)](https://gitter.im/vim-ale/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 
 ![ALE Logo by Mark Grealish - https://www.bhalash.com/](https://user-images.githubusercontent.com/3518142/59195920-2c339500-8b85-11e9-9c22-f6b7f69637b8.jpg)

doc/ale-development.txt

@@ -148,13 +148,14 @@ Apply the following rules when writing Bash scripts.
 ===============================================================================
 4. Testing ALE              *ale-development-tests* *ale-dev-tests* *ale-tests*
 
-ALE is tested with a suite of tests executed in Travis CI and AppVeyor. ALE
-runs tests with the following versions of Vim in the following environments.
+ALE is tested with a suite of tests executed via GitHub Actions and AppVeyor.
+ALE runs tests with the following versions of Vim in the following
+environments.
 
-1. Vim 8.0.0027 on Linux via Travis CI.
-2. Vim 8.1.0519 on Linux via Travis CI.
-3. NeoVim 0.2.0 on Linux via Travis CI.
-4. NeoVim 0.3.5 on Linux via Travis CI.
+1. Vim 8.0.0027 on Linux via GitHub Actions.
+2. Vim 8.2.2401 on Linux via GitHub Actions.
+3. NeoVim 0.2.0 on Linux via GitHub Actions.
+4. NeoVim 0.4.4 on Linux via GitHub Actions.
 5. Vim 8 (stable builds) on Windows via AppVeyor.
 
 If you are developing ALE code on Linux, Mac OSX, or BSD, you can run ALEs
@@ -192,7 +193,8 @@ tests.
 
 When you add new linters or fixers, make sure to add them into the tables in
 supported-tools.md and |ale-supported-languages-and-tools.txt|. If you forget to
-keep them both in sync, you should see an error like the following in Travis CI.
+keep them both in sync, you should see an error like the following in the
+builds run for GitHub Actions.
 >
   ========================================
   diff supported-tools.md and doc/ale-supported-languages-and-tools.txt tables

test/script/custom-linting-rules

@@ -143,8 +143,8 @@ check_errors '\(!=.\?\|isnot\) type({})' "Use 'isnot v:t_dict' instead"
 check_errors '\(!=.\?\|isnot\) type(function([^)]\+))' "Use 'isnot v:t_func' instead"
 
 # Run a Python script to find lines that require padding around them.  For
-# users without Python installed, we'll skip these checks. Travis CI will run
-# the script.
+# users without Python installed, we'll skip these checks. GitHub Actions will
+# run the script.
 if command -v python > /dev/null; then
     if ! test/script/block-padding-checker "$directory"/**/*.vim; then
         RETURN_CODE=1