Fix up checks in Makefile and make them portable

.gitattributes

@@ -1,2 +1,3 @@
 test/fixtures/* eol=lf
-init-tests-after-clone.sh
+*.sh eol=lf
+/Makefile eol=lf

.gitignore

@@ -1,6 +1,8 @@
 *.py[co]
 *.swp
 *~
+.env/
+env/
 .venv/
 venv/
 /*.egg-info

Makefile

@@ -7,16 +7,10 @@ clean:
 	rm -rf build/ dist/ .eggs/ .tox/
 
 release: clean
-	# Check if latest tag is the current head we're releasing
-	echo "Latest tag = $$(git tag | sort -nr | head -n1)"
-	echo "HEAD SHA       = $$(git rev-parse head)"
-	echo "Latest tag SHA = $$(git tag | sort -nr | head -n1 | xargs git rev-parse)"
-	@test "$$(git rev-parse head)" = "$$(git tag | sort -nr | head -n1 | xargs git rev-parse)"
+	./check-version.sh
 	make force_release
 
 force_release: clean
-	# IF we're in a virtual environment, add build tools
-	test -z "$$VIRTUAL_ENV" || pip install -U build twine
-	python3 -m build --sdist --wheel || echo "Use a virtual-env with 'python -m venv env && source env/bin/activate' instead"
+	./build-release.sh
 	twine upload dist/*
 	git push --tags origin main

build-release.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+#
+# This script builds a release. If run in a venv, it auto-installs its tools.
+# You may want to run "make release" instead of running this script directly.
+
+set -eEu
+
+function release_with() {
+    $1 -m build --sdist --wheel
+}
+
+if test -n "${VIRTUAL_ENV:-}"; then
+    deps=(build twine)  # Install twine along with build, as we need it later.
+    echo "Virtual environment detected. Adding packages: ${deps[*]}"
+    pip install --quiet --upgrade "${deps[@]}"
+    echo 'Starting the build.'
+    release_with python
+else
+    function suggest_venv() {
+        venv_cmd='python -m venv env && source env/bin/activate'
+        printf "HELP: To avoid this error, use a virtual-env with '%s' instead.\n" "$venv_cmd"
+    }
+    trap suggest_venv ERR  # This keeps the original exit (error) code.
+    echo 'Starting the build.'
+    release_with python3 # Outside a venv, use python3.
+fi

check-version.sh

@@ -0,0 +1,46 @@
+#!/bin/bash
+#
+# This script checks if we are in a consistent state to build a new release.
+# See the release instructions in README.md for the steps to make this pass.
+# You may want to run "make release" instead of running this script directly.
+
+set -eEfuo pipefail
+trap 'echo "$0: Check failed. Stopping." >&2' ERR
+
+readonly version_path='VERSION'
+readonly changes_path='doc/source/changes.rst'
+
+echo 'Checking current directory.'
+test "$(cd -- "$(dirname -- "$0")" && pwd)" = "$(pwd)"  # Ugly, but portable.
+
+echo "Checking that $version_path and $changes_path exist and have no uncommitted changes."
+test -f "$version_path"
+test -f "$changes_path"
+git status -s -- "$version_path" "$changes_path"
+test -z "$(git status -s -- "$version_path" "$changes_path")"
+
+# This section can be commented out, if absolutely necessary.
+echo 'Checking that ALL changes are committed.'
+git status -s --ignore-submodules
+test -z "$(git status -s --ignore-submodules)"
+
+version_version="$(cat "$version_path")"
+changes_version="$(awk '/^[0-9]/ {print $0; exit}' "$changes_path")"
+config_opts="$(printf ' -c versionsort.suffix=-%s' alpha beta pre rc RC)"
+latest_tag="$(git $config_opts tag -l '[0-9]*' --sort=-v:refname | head -n1)"
+head_sha="$(git rev-parse HEAD)"
+latest_tag_sha="$(git rev-parse "$latest_tag")"
+
+# Display a table of all the current version, tag, and HEAD commit information.
+echo $'\nThe VERSION must be the same in all locations, and so must the HEAD and tag SHA'
+printf '%-14s = %s\n' 'VERSION file'   "$version_version" \
+                      'changes.rst'    "$changes_version" \
+                      'Latest tag'     "$latest_tag" \
+                      'HEAD SHA'       "$head_sha" \
+                      'Latest tag SHA' "$latest_tag_sha"
+
+# Check that the latest tag and current version match the HEAD we're releasing.
+test "$version_version" = "$changes_version"
+test "$latest_tag" = "$version_version"
+test "$head_sha" = "$latest_tag_sha"
+echo 'OK, everything looks good.'