Change database dump format + add import & export scripts

The new format allows for downloading and importing only a part of the
database - useful when only the metadata is required - and doesn't
include the wasteful preformatted HTML cache.

This also ensures that the new import.sql script is actually usable and
in sync with the actual database. The old schema.sql was neither.

(And this simplifies my backup scripts)

util/export.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+
+set -e
+
+mkdir -p ../dl
+
+# Only run once a week
+[ -e ../dl/current ] && [ -z $(find ../dl/current -daystart -mtime +7) ] && exit
+
+# Only keep the last dump
+rm -rf $(printf '%s\n' ../dl/????-??-?? | sort | head -n -1)
+
+# Create a new dump
+OUT=../dl/.work
+export OUT
+rm -fr $OUT
+mkdir -p $OUT
+
+cp ../import.sql $OUT/import.sql
+
+psql -wqU manned <<EOF
+\copy systems          to program 'zstd - -qo $OUT/systems.tsv.zst'
+\copy contents (id, hash, content) to program 'zstd - -qo $OUT/contents.tsv.zst'
+\copy mans             to program 'zstd - -qo $OUT/mans.tsv.zst'
+\copy locales          to program 'zstd - -qo $OUT/locales.tsv.zst'
+\copy encodings        to program 'zstd - -qo $OUT/encodings.tsv.zst'
+\copy packages         to program 'zstd - -qo $OUT/packages.tsv.zst'
+\copy package_versions to program 'zstd - -qo $OUT/package_versions.tsv.zst'
+\copy files            to program 'zstd - -qo $OUT/files.tsv.zst'
+EOF
+
+DATE=$(date +%F)
+mv -T $OUT ../dl/$DATE
+echo $DATE >../dl/current