Add config script to be used with GitHub Actions

scripts/config.sh

@@ -0,0 +1,64 @@
+#!/bin/sh
+
+usage ()
+{
+    printf 'Generate parameters for GitHub Actions\n\n'
+    printf 'Usage:\n\t%s <pandoc_version> <build_stack> <image_name>\n' "$0"
+}
+
+if [ "$#" -ne 3 ]; then
+    usage
+    exit 1
+fi
+
+version="${1:-main}"
+build_stack="${2:-alpine}"
+image_name="${3:-pandoc/minimal}"
+
+versions_file=versions.md
+row="$(grep "^| $version " "$versions_file")"
+
+if [ -z "$row" ]; then
+    printf "Unknown or unsupported version '%s'\n" "$version"
+    exit 1
+fi
+
+field ()
+{
+    col=$(($1 + 1))
+    printf '%s\n' "$row" | \
+        awk -F '|' "{ gsub(/^ *| *\$/,\"\",\$$col); print \$${col} }" | \
+        sed -e 's/  */,/g'
+}
+
+case "${build_stack}" in
+    (alpine|static)
+        base_image='alpine'
+        base_image_tag="$(field 3)"
+        ;;
+    (ubuntu)
+        base_image='ubuntu'
+        base_image_tag="$(field 4)"
+        ;;
+    (*)
+        printf "Unsupported base image: '%s'\n" "$base_image"
+        ;;
+esac
+
+printf '%s\n' "$(field 2)"
+
+tagsbase="$(field 2 | sed -e "s#\([^,]*\)#${image_name}:\1#g")"
+tags="$(printf '%s' "$tagsbase" | \
+               sed -e 's#\([^,]*\)#\1-'${base_image}'#g')"
+if ( [ "$image_name" != 'pandoc/minimal' ] && \
+     [ "$build_stack" = 'alpine' ] ) ||
+   ( [ "$image_name"  = 'pandoc/minimal' ] && \
+     [ "$build_stack" = 'static' ] );
+then
+    tags="${tags},${tagsbase}"
+fi
+
+printf 'tags="%s"\n' "$tags"
+printf 'base_image="%s"\n' "$base_image"
+printf 'base_image_tag="%s"\n' "$base_image_tag"
+printf 'texlive_version="%s"\n' "$(field 5)"