Use a .travis.sh script

.travis.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+
+set -e
+
+# install GHCs
+./ghcup.sh -v install 8.2.2
+./ghcup.sh -v install 8.4.3
+./ghcup.sh -v install 8.6.1
+
+# set GHC
+./ghcup.sh -v set 8.6.1
+./ghcup.sh -v set 8.4.3
+
+# install cabal-install
+wget https://www.haskell.org/cabal/release/cabal-install-2.2.0.0/cabal-install-2.2.0.0-x86_64-unknown-linux.tar.gz
+tar -xzf cabal-install-2.2.0.0-x86_64-unknown-linux.tar.gz
+
+export PATH="$HOME/.ghcup/bin:$PATH"
+
+# install shellcheck
+./cabal new-update
+./cabal new-install ShellCheck
+
+# check our script for errors
+~/.cabal/bin/shellcheck ghcup.sh

.travis.yml

@@ -5,16 +5,7 @@ sudo: false
 
 # TODO: also run checkbashisms.pl (currently two instances of non-compliance)
 script:
- - ./ghcup.sh -v install 8.2.2
- - ./ghcup.sh -v install 8.4.3
- - ./ghcup.sh -v install 8.6.1
- - ./ghcup.sh -v set 8.6.1
- - ./ghcup.sh -v set 8.4.3
- - wget https://www.haskell.org/cabal/release/cabal-install-2.2.0.0/cabal-install-2.2.0.0-x86_64-unknown-linux.tar.gz
- - tar -xzf cabal-install-2.2.0.0-x86_64-unknown-linux.tar.gz
- - ./cabal new-update
- - ./cabal new-install ShellCheck
- - ~/.cabal/bin/shellcheck ghcup.sh
+ - ./.travis.sh
 
 matrix:
   fast_finish: true