[#6] Add automated database updater

A small parser of unece.org "Trade code download page" added to Makefile to fetch last
database's URL to download. Also, the forgejo action added. Action runs every
month to update databases and send PR to Forgejo.

Signed-off-by: George Bartolomey <george@bh4.ru>

.forgejo/workflows/updatechecker.yml

@@ -0,0 +1,17 @@
+on:
+  schedule:
+    - cron: "2 0 1 * *"
+jobs:
+  checkupdates:
+    runs-on: docker
+    steps:
+      - uses: https://code.forgejo.org/actions/checkout@v3
+      - run: make update
+      - run: |
+          git config user.name "Snegurochka"
+          git config user.email "snegurochka@frostfs.info"
+          git switch -c update-dbs
+          git add .
+          git remote set-url origin https://x-access-token:${{ secrets.GITHUB_TOKEN }}@git.frostfs.info/TrueCloudLab/frostfs-locode-db
+          git commit -m "Automatic database update (UN/LOCODE version $(cat tmp/locode-version.txt))" && \
+          git push origin HEAD:refs/for/master -o topic=automatic-database-update

Makefile

@@ -63,7 +63,10 @@ data/countries.dat.gz: $(DIRS)
 # IGNORE
 # See https://unece.org/trade/cefact/UNLOCODE-Download
 tmp/locode.csv.zip :$(DIRS)
-	wget -c https://service.unece.org/trade/locode/loc222csv.zip -O tmp/locode.csv.zip
+	DOWNLOADURL=$$(wget -O - https://unece.org/trade/cefact/UNLOCODE-Download \
+		| grep -oP '(?<=href=")\S+loc\d+csv\.zip'); \
+	echo "$$DOWNLOADURL" | grep -oP '(?<=loc)\d+' > tmp/locode-version.txt; \
+	wget -c "$$DOWNLOADURL" -O tmp/locode.csv.zip
 
 data/unlocode-SubdivisionCodes.csv.gz: tmp/locode.csv.zip
 	unzip -p tmp/locode.csv.zip "*SubdivisionCodes.csv" | gzip > data/unlocode-SubdivisionCodes.csv.gz