Improve readme

README.md

@@ -1,5 +1,33 @@
 # yore
 
+## Development
+
+`flake.nix` defines a development shell that has everything you'll need. To enter, run
+
+```
+nix develop
+```
+
+The rest of this section assumes you're in the dev shell.
+
+### Running Postgres
+
+`scripts/with-db $COMMAND` will create a Postgres cluster in a temporary directory with the credentials `user=yore-test dbname=yore-test port=5433`, start the Postgres server, run `$COMMAND` and then stop the Postgres erver.
+On Linux, you need to have write permissions vor `/var/run/postgresql` to run it.
+You can use this to run the tests in an entirely fresh database, e.g.:
+
+```
+scripts/with-db cabal test
+```
+
+You can also use it to run a database for development by choosing a `$COMMAND` that runs until you quit it, e.g.
+
+```
+BASE_DIR=./pgdata scripts/with-db psql "dbname=yore-test port=5433 user=yore-test"
+```
+
+By setting `$BASE_DIR` you can persist the database for later runs.
+
 ## Inspo
 
 - https://fz.ub.uni-freiburg.de/show/fz.cgi?pKuerzel=FZ
@@ -7,6 +35,7 @@
     - So we're gonna do the PDFs after all
     - Let's hope we can deduce the PDF path from the link
     - And also that the PDFs aren't generated on demand as well.
+      - They are actually
 
 ## TODO