feat(CI): add the GitHub Super Linter

The GitHub Super Linter is a more robust and better supported
tool than the current GitHub Actions we are using.

Running these checks:

ERROR_ON_MISSING_EXEC_BIT: true
VALIDATE_BASH: true
VALIDATE_BASH_EXEC: true
VALIDATE_EDITORCONFIG: true
VALIDATE_MARKDOWN: true
VALIDATE_SHELL_SHFMT: true
VALIDATE_YAML: true

https://github.com/marketplace/actions/super-linter
https://github.com/github/super-linter

Added the GitHub Super Linter badge to the README.

Also updated the pre-commit framework and added
more documentation on pre-commit.

Added one more pre-commit check: check-executables-have-shebangs

Added one extra check for merge conflicts to our
GitHub Actions.

EditorConfig and Markdown linting.

Minor grammar and spelling fixes.

Update linter.yml

5 files changed, 17 insertions, 18 deletions

diff --git a/test/assert.rb b/test/assert.rb
index 73382fb1c..8cd2b375b 100644
--- a/test/assert.rb
+++ b/test/assert.rb
@@ -290,7 +290,7 @@ def assert_float(exp, act, msg = nil)
   if e.finite? && a.finite? && (n = (e - a).abs) > Mrbtest::FLOAT_TOLERANCE
     flunk(msg, "    Expected |#{exp} - #{act}| (#{n}) to be <= #{Mrbtest::FLOAT_TOLERANCE}.")
   elsif (e.infinite? || a.infinite?) && e != a ||
-     e.nan? && !a.nan? || !e.nan? && a.nan?
+    e.nan? && !a.nan? || !e.nan? && a.nan?
     flunk(msg, "    Expected #{act} to be #{exp}.")
   else
     pass
diff --git a/test/t/literals.rb b/test/t/literals.rb
index b7b07cd9d..f93968650 100644
--- a/test/t/literals.rb
+++ b/test/t/literals.rb
@@ -90,7 +90,7 @@ assert('Literals Strings Here documents', '8.7.6.3.6') do
   a = <<AAA
 aaa
 AAA
-   b = <<b_b
+  b = <<b_b
 bbb
 b_b
     c = [<<CCC1, <<"CCC2", <<'CCC3']
@@ -250,7 +250,6 @@ ZZZ
   assert_equal ["1", "www\n", "3", "4", "5"], w
   assert_equal [1, "foo 222 333\n 444\n5\n bar\n6\n", 9], x
   assert_equal "", z
-
 end
 
 
diff --git a/test/t/module.rb b/test/t/module.rb
index 07d550804..9aa018280 100644
--- a/test/t/module.rb
+++ b/test/t/module.rb
@@ -391,15 +391,15 @@ assert('Module#undef_method', '15.2.2.4.42') do
     class Parent
       def hello
       end
-     end
+    end
 
-     class Child < Parent
+    class Child < Parent
       def hello
       end
-     end
+    end
 
-     class GrandChild < Child
-     end
+    class GrandChild < Child
+    end
   end
   Test4UndefMethod::Child.class_eval{ undef_method :hello }
 
@@ -736,9 +736,9 @@ assert('Issue 1467') do
 
   class C1
     include M1
-     def initialize()
-       super()
-     end
+      def initialize()
+        super()
+      end
   end
 
   class C2
diff --git a/test/t/nameerror.rb b/test/t/nameerror.rb
index 28682bedc..9d2e2a470 100644
--- a/test/t/nameerror.rb
+++ b/test/t/nameerror.rb
@@ -20,9 +20,9 @@ assert('NameError#name', '15.2.31.2.1') do
 end
 
 assert('NameError#initialize', '15.2.31.2.2') do
-   e = NameError.new('a', :foo)
+  e = NameError.new('a', :foo)
 
-   assert_equal NameError, e.class
-   assert_equal 'a', e.message
-   assert_equal :foo, e.name
+  assert_equal NameError, e.class
+  assert_equal 'a', e.message
+  assert_equal :foo, e.name
 end
diff --git a/test/t/string.rb b/test/t/string.rb
index c1511de63..447493227 100644
--- a/test/t/string.rb
+++ b/test/t/string.rb
@@ -148,9 +148,9 @@ assert('String#[]=') do
   end
 
   if Object.const_defined?(:Float)
-   e = 'abc'
-   e[1.1] = 'X'
-   assert_equal 'aXc', e
+    e = 'abc'
+    e[1.1] = 'X'
+    assert_equal 'aXc', e
   end
 
   assert_raise(TypeError) { 'a'[0] = 1 }