refactor: use .python-version for docker build

scripts/docker-build

@@ -6,20 +6,41 @@ cd "$RUN_DIR"
 
 builddir=build
 
+_latest_python_version() {
+    filter="$1"
+    filter_regex=$(echo "$filter" | sed 's/\./\\\\./')
+    curl -sfL https://api.github.com/repos/python/cpython/git/refs/tags \
+    | jq -r 'map(select(.ref | test("^refs/tags/v?'"$filter_regex"'($|\\.)")) | .ref | match("refs/tags/v?(.*)").captures[0].string)[]' \
+    | grep -xE '[.0-9]+' \
+    | sort --version-sort \
+    | tail -n 1
+}
+
 [ -z "${DEBUG:-}" ] || set -x
 
 mkdir -p "$builddir"
 
+python_version_filter=$(cat .python-version)
+python_version=$(_latest_python_version "$python_version_filter")
+
+if [ -z "$python_version" ]; then
+    echo >&2 "No Python version found matching the filter: $python_version_filter"
+    exit 1
+fi
+
+githash_short=$(git rev-parse --short HEAD)
+githash_long=$(git rev-parse HEAD)
+version="$githash_short"
+echo "$version" >"$builddir"/version
+
 poetry export \
     --with=build \
     --output="$builddir"/requirements.txt
 
-githash=$(git rev-parse --short HEAD)
-today=$(date -u '+%Y.%m.%d')
-version="${today}+${githash}"
-echo "$version" >"$builddir"/version
-
 $DOCKER_BIN build \
     --pull \
-    --tag "code.dumpr.org/ducklet/unwind":"$version" \
+    --build-arg="PYTHON_VERSION=$python_version" \
+    --label="python.version=$python_version" \
+    --label="git.hash=$githash_long" \
+    --tag="code.dumpr.org/ducklet/unwind":"$version" \
     .