Add script and instructions to apply local migrations. (#58)

* make: add `make apply_migration name=folder-name` entrypoint.
* docs: add README instructions to apply migrations.

Makefile

@@ -71,3 +71,6 @@ shell:
 
 shell_clean:
 	iex -S mix run --no-start
+
+apply_migration:
+	./apply-local-migration.sh $(name)

README.md

@@ -20,7 +20,7 @@ It's an Elixir application that integrates with Postgres over logical replicatio
 
 ## Pre-reqs
 
-Docker and Elixir 1.13.
+Docker and [Elixir 1.14 compiled with Erlang 24](https://thinkingelixir.com/install-elixir-using-asdf/).
 
 ## Usage
 
@@ -48,7 +48,7 @@ And then develop using:
 make shell
 ```
 
-This runs active-active replication with Postgres over logical replication and exposes a protocol buffers API over web sockets on `localhost:30002` for the ElectricSQL client libraries.
+This runs active-active replication with Postgres over logical replication and exposes a protocol buffers API over web sockets on `localhost:5133`.
 
 For example to write some data into one of the Postgres instances:
 
@@ -58,6 +58,38 @@ docker exec -it -e PGPASSWORD=password electric_db_a_1 psql -h 127.0.0.1 -U elec
 
 There's a second instance, `electric-db_b_1`, if you want to see data being replicated between them.
 
+Note that you can tear down all the containers with:
+
+```sh
+make stop_dev_env
+```
+
+## Migrations
+
+When running locally, you can apply migrations directly using `make apply_migration`. First make sure you've [built your migrations](https://electric-sql.com/docs/usage/migrations) in your application folder, then set the `ELECTRIC_MIGRATIONS_DIR` environment variable to the path to the migrations folder:
+
+```sh
+export ELECTRIC_MIGRATIONS_DIR='../path/to/migrations'
+```
+
+Now (re)run the electric service (with the env var set):
+
+```sh
+make shell
+```
+
+You can now apply named migrations using:
+
+```sh
+make apply_migration $MIGRATION_NAME
+```
+
+Where `MIGRATION_NAME` is the name of a migration folder created using [`electric migrations new`](https://electric-sql.com/docs/usage/migrations#2-schema-evolution), for example:
+
+```sh
+make apply_migration 1666288253_create_items
+```
+
 ## OSX
 
 Note that if, when running on OSX, you get errors like:

apply-local-migration.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+set -e
+
+if [ -z "$1" ]
+  then
+    echo "Specify the migration using \`make apply_migration name=<migration folder name>\`."
+
+    exit 1
+fi
+
+data="{\"vsn\":\"$1\"}"
+json='Content-Type: application/json'
+
+curl -v -X PUT http://localhost:5050/api/migrations/postgres_1 -H $json -d $data
+curl -v -X PUT http://localhost:5050/api/migrations/postgres_2 -H $json -d $data