Simplify CI

- Remove cabal-plan, we actually never call it (I think)
- Remove vendored cabal-doctest
- Remove few stray allow-newer clauses no longer necessary, apparently

Originally done by @gbaz in PR haskell#7907.

.github/workflows/linux.yml

@@ -54,15 +54,6 @@ jobs:
         run: |
           echo "$HOME/.cabal/bin" >> $GITHUB_PATH
 
-      - name: Install cabal-plan
-        run: |
-          mkdir -p $HOME/.cabal/bin
-          curl -sL 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 > $HOME/.cabal/bin/cabal-plan
-          rm -f cabal-plan.xz
-          chmod a+x $HOME/.cabal/bin/cabal-plan
-
       - name: Update Hackage index
         run: cabal v2-update
 

.github/workflows/macos.yml

@@ -33,12 +33,6 @@ jobs:
       - name: Update Hackage index
         run: cabal v2-update
 
-      - name: Install cabal-plan
-        run: |
-          cd $(mktemp -d)
-          # aeson +fast, so we don't wait for -O2
-          cabal v2-install cabal-plan --constraint='cabal-plan ^>=0.6.2.0' --constraint='aeson +fast' --constraint='cabal-plan +exe'
-
       - uses: actions/checkout@v2
 
       - name: Validate print-config

cabal.project

@@ -11,20 +11,11 @@ packages: Cabal-described
 packages: Cabal-tests/
 packages: cabal-benchmarks/
 
-packages: vendor/cabal-doctest-1.0.8
-
 optional-packages: ./vendored/*/*.cabal
 
--- Remove after hackage-repo-tool release
-allow-newer:
-  hackage-repo-tool:optparse-applicative
-
 allow-newer:
   hackage-security:Cabal
 
--- https://github.com/haskell-hvr/windns/pull/2
-allow-newer: windns-0.1.0.1:base
-
 -- avoiding extra dependencies
 constraints: rere -rere-cfg
 constraints: these -assoc

cabal.project.coverage

@@ -11,8 +11,6 @@ packages: Cabal-described
 packages: Cabal-tests/
 packages: cabal-benchmarks/
 
-packages: vendor/cabal-doctest-1.0.8
-
 -- Uncomment to allow picking up extra local unpacked deps:
 --optional-packages: */
 

cabal.project.libonly

@@ -5,8 +5,6 @@ packages: Cabal-tree-diff
 packages: Cabal-described
 packages: Cabal-tests
 
-packages: vendor/cabal-doctest-1.0.8
-
 tests: True
 
 -- Uncomment to allow picking up extra local unpacked deps:

cabal.project.validate

@@ -11,8 +11,6 @@ packages: Cabal-described
 packages: Cabal-tests
 packages: cabal-benchmarks
 
-packages: vendor/cabal-doctest-1.0.8
-
 tests: True
 
 -- avoiding extra dependencies

cabal.project.validate.libonly

@@ -6,8 +6,6 @@ packages: Cabal-tree-diff
 packages: Cabal-described
 packages: Cabal-tests
 
-packages: vendor/cabal-doctest-1.0.8
-
 tests: True
 
 write-ghc-environment-files: never