maintainers/scripts/haskell: Improve commit messages

maintainers/scripts/haskell/update-stackage.sh

@@ -4,11 +4,21 @@ set -eu -o pipefail
 
 tmpfile=$(mktemp "update-stackage.XXXXXXX")
 # shellcheck disable=SC2064
+
+config_file="pkgs/development/haskell-modules/configuration-hackage2nix.yaml"
+
 trap "rm ${tmpfile} ${tmpfile}.new" 0
+touch "$tmpfile" "$tmpfile.new" # Creating files here so that trap creates no errors.
 
 curl -L -s "https://stackage.org/nightly/cabal.config" >"$tmpfile"
+old_version=$(grep "  # Stackage Nightly" $config_file | sed -E 's/.*([0-9]{4}-[0-9]{2}-[0-9]{2}).*/\1/')
 version=$(sed -rn "s/^--.*http:..(www.)?stackage.org.snapshot.nightly-//p" "$tmpfile")
 
+if [[ "$old_version" == "$version" ]]; then
+   echo "No new stackage version"
+   exit 0 # Nothing to do
+fi
+
 # Create a simple yaml version of the file.
 sed -r \
     -e '/^--/d' \
@@ -43,14 +53,18 @@ sed -r \
 # Drop the previous configuration ...
 # shellcheck disable=SC1004
 sed -e '/  # Stackage Nightly/,/^$/c \TODO\
-'   -i pkgs/development/haskell-modules/configuration-hackage2nix.yaml
+'   -i $config_file
 
 # ... and replace it with the new one.
 sed -e "/TODO/r $tmpfile" \
     -e "s/TODO/  # Stackage Nightly $version/" \
-    -i pkgs/development/haskell-modules/configuration-hackage2nix.yaml
+    -i $config_file
 
 if [[ "${1:-}" == "--do-commit" ]]; then
-   git add pkgs/development/haskell-modules/configuration-hackage2nix.yaml
-   git commit -m "configuration-hackage2nix.yaml: Changing Stackage pin to Nightly $version"
+git add $config_file
+git commit -F - << EOF
+Stackage Nightly: $old_version -> $version
+
+This commit has been generated by maintainers/scripts/haskell/update-stackage.sh
+EOF
 fi