ci: Drop support for GHC 8.4

Debian stable and Ubuntu 20.04 are now 8.8 and 8.6, respectively, which
was always our guide as to which GHC versions we want to support.

.github/workflows/haskell-ci.yml

@@ -66,11 +66,6 @@ jobs:
             compilerVersion: 8.6.5
             setup-method: hvr-ppa
             allow-failure: false
-          - compiler: ghc-8.4.4
-            compilerKind: ghc
-            compilerVersion: 8.4.4
-            setup-method: hvr-ppa
-            allow-failure: false
       fail-fast: false
     steps:
       - name: apt

.github/workflows/stack.yml

@@ -12,10 +12,8 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - resolver: lts-12  # GHC 8.4
+          - resolver: lts-14  # GHC 8.6
             yaml: stack.yaml
-          - resolver: lts-12  # GHC 8.4
-            yaml: stack-master.yaml
           - resolver: lts-14  # GHC 8.6
             yaml: stack-master.yaml
           - resolver: lts-16  # GHC 8.8

CHANGES.md

@@ -4,6 +4,8 @@
 
 ### Breaking Changes
 
+  * Dropped support for GHC 8.4.
+
   * `XMonad.Util.ExclusiveScratchpads`
 
     - Deprecated the module in favour of the (new) exclusive scratchpad

xmonad-contrib.cabal

@@ -38,7 +38,7 @@ cabal-version:      1.12
 build-type:         Simple
 bug-reports:        https://github.com/xmonad/xmonad-contrib/issues
 
-tested-with:        GHC == 8.4.4 || == 8.6.5 || == 8.8.4 || == 8.10.7 || == 9.0.2 || == 9.2.5 || == 9.4.2
+tested-with:        GHC == 8.6.5 || == 8.8.4 || == 8.10.7 || == 9.0.2 || == 9.2.5 || == 9.4.2
 
 source-repository head
   type:     git
@@ -79,7 +79,7 @@ library
        ghc-options: -Werror -Wwarn=deprecations -Wwarn=dodgy-imports
 
     -- Keep this in sync with the oldest version in 'tested-with'
-    if impl(ghc > 8.4.4)
+    if impl(ghc > 8.6.5)
        -- don't treat unused-imports warning as errors, they may be necessary
        -- for compatibility with older versions of base (or other deps)
        ghc-options: -Wwarn=unused-imports
@@ -480,7 +480,7 @@ test-suite tests
      ghc-options: -Werror -Wwarn=deprecations -Wwarn=dodgy-imports
 
   -- Keep this in sync with the oldest version in 'tested-with'
-  if impl(ghc > 8.4.4)
+  if impl(ghc > 8.6.5)
      -- don't treat unused-imports warning as errors, they may be necessary
      -- for compatibility with older versions of base (or other deps)
      ghc-options: -Wwarn=unused-imports