GHC-8.10 support for 3.2

Includes cherry-picked commits:

- Test cabal-install with GHC-8.10 haskell#6709
- Add GHC-8.10.1 job. Only tests Cabal-the-lib part atm. haskell#6617

Also add topHandler' signature.

.docker/validate-8.10.1.dockerfile

@@ -0,0 +1,60 @@
+FROM    phadej/ghc:8.10.1-bionic
+
+# Install cabal-plan
+RUN     mkdir -p /root/.cabal/bin && \
+        curl -L https://github.com/haskell-hvr/cabal-plan/releases/download/v0.6.2.0/cabal-plan-0.6.2.0-x86_64-linux.xz > cabal-plan.xz && \
+        echo "de73600b1836d3f55e32d80385acc055fd97f60eaa0ab68a755302685f5d81bc  cabal-plan.xz" | sha256sum -c - && \
+        xz -d < cabal-plan.xz > /root/.cabal/bin/cabal-plan && \
+        rm -f cabal-plan.xz && \
+        chmod a+x /root/.cabal/bin/cabal-plan
+
+# Update index
+RUN     cabal v2-update
+
+# We install happy, so it's in the store; we (hopefully) don't use it directly.
+RUN     cabal v2-install happy --constraint 'happy ^>=1.19.12'
+
+# Install some other dependencies
+# Remove $HOME/.ghc so there aren't any environments
+RUN     cabal v2-install -w ghc-8.10.1 --lib \
+          aeson \
+          async \
+          base-compat \
+          base16-bytestring \
+          base64-bytestring \
+          cryptohash-sha256 \
+          Diff \
+          echo \
+          ed25519 \
+          edit-distance \
+          haskell-lexer \
+          HTTP \
+          network \
+          optparse-applicative \
+          pretty-show \
+          regex-compat-tdfa \
+          regex-tdfa \
+          statistics \
+          tar \
+          tasty \
+          tasty-golden \
+          tasty-hunit \
+          tasty-quickcheck \
+          tree-diff \
+          zlib \
+      --constraint="bytestring installed" \
+      --constraint="binary     installed" \
+      --constraint="containers installed" \
+      --constraint="deepseq    installed" \
+      --constraint="directory  installed" \
+      --constraint="filepath   installed" \
+      --constraint="pretty     installed" \
+      --constraint="process    installed" \
+      --constraint="time       installed" \
+      --constraint="unix       installed" \
+        && rm -rf $HOME/.ghc
+
+# Validate
+WORKDIR /build
+COPY    . /build
+RUN     sh ./validate.sh -w ghc-8.10.1 -v

.github/workflows/artifacts.yml

@@ -25,7 +25,7 @@ jobs:
           echo "::add-path::$HOME/.cabal/bin"
       - name: Update Hackage index
         run: cabal v2-update
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: Release project
         run: |
           cp cabal.project.release cabal.project
@@ -71,7 +71,7 @@ jobs:
           echo "::add-path::$HOME/.cabal/bin"
       - name: Update Hackage index
         run: cabal v2-update
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: Release project
         run: |
           cp cabal.project.release cabal.project
@@ -115,7 +115,7 @@ jobs:
           cabal user-config init -a "http-transport: plain-http" -a "store-dir: C:\SR" -f -v3
       - name: Update Hackage index
         run: cabal v2-update
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: Release project
         shell: bash
         run: |

.github/workflows/bootstrap.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Set PATH
         run: |
           echo "::add-path::/opt/ghc/8.6.5/bin"
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: bootstrap.sh
         env:
           EXTRA_CONFIGURE_OPTS: ""
@@ -53,7 +53,7 @@ jobs:
         run: |
           echo "::add-path::/opt/ghc/8.6.5/bin"
           echo "::add-path::$HOME/.cabal/bin"
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: bootstrap.sh
         env:
           EXTRA_CONFIGURE_OPTS: ""