Abel fork of Haskell-CI

This combines all the changes wrt. the original Haskell-CI into one
commit, so that it can more easily be rebased onto the changes in the original.

* README: clarify the relation of this fork to the original

* Use 9.8.0 for GHC 9.8.1-alpha4

* Switch default distro to focal; use actions/checkout@v4 when possible

  `actions/checkout@v4` does not work with `bionic` (18.04).
  So we switch to `focal` (20.04), dropping most of GHC 7 support.
  GHC 7.10.3 is still supported, and 7.4.2, 7.2.2 and 7.0.4.

  Addresses haskell-CI#628

* Bump version to 0.17.today

Makefile

@@ -1,4 +1,4 @@
-HC ?= ghc-9.2.7
+HC ?= ghc-9.4.7
 
 build :
 	cabal v2-build -w $(HC)

README.md

@@ -1,3 +1,19 @@
+Note: this is a fork of https://github.com/haskell-CI/haskell-ci, rebased on the original.
+
+Change(s) in this fork:
+
+- Use `.0` for GHC prereleases instead of `.1`.
+  E.g. here you declare `tested-with: GHC == 9.8.0` to get CI for a prerelease of GHC 9.8.
+  In the original, you declare `tested-with: GHC == 9.8.1`.
+  See: https://github.com/haskell-CI/haskell-ci/issues/631
+
+- Default distribution is `focal` instead of `bionic`.
+  So, consistently only GHC 7.10.3 and up are supported.
+  See: https://github.com/haskell-CI/haskell-ci/issues/628.
+
+Full change set at: https://github.com/haskell-CI/haskell-ci/compare/master...andreasabel:haskell-ci:master
+
+
 haskell-ci - CI generator for multiple [GHC](http://haskell.org/ghc) versions
 =============================================================================
 
@@ -40,7 +56,7 @@ GHC-7.0.1 — GHC-9.6.1 are supported.
     Tested-With: GHC ==8.6.5 || ==8.4.4 || ==8.2.2
     ...
     ```
-    
+
     Add as many or as few GHC versions to test as you want.
 
 * Step 4: Generate a workflow file for your project:
@@ -71,30 +87,30 @@ GHC-7.0.1 — GHC-9.6.1 are supported.
     $ git commit -m "New CI script"
     $ git push -u origin new-ci      # Push your branch upstream
     ```
-    
+
 * Step 6: Fix the build
 
     If you're lucky, your repository will build for every compiler version
     you listed.  If that's the case, then just merge your changes into `master`:
-    
+
     ```bash
     $ git checkout master
     $ git merge new-ci  # Update `master` with your new CI script
     $ git push
     ```
-    
+
     You can also merge your branch into `master` from Github's pull request view.
-    
+
     If you're not lucky, then your new CI branch will fail for one or more
     versions of GHC, which is okay!  Look at the build and fix any build failures
     you find and commit the fixes to your branch:
-    
+
     ```bash
     $ # Fix any build failures you find and commit your changes
     $ ...
     $ git push  # Push your branch updates upstream
     ```
-    
+
     Sometimes you may need to regenerate CI script, for example, when
     adding new compiler version to `tested-with`.
     You may simply run `haskell-ci regenerate`.