Add PGXN release workflow

PGXN requires a `META.json` file, so add it and a `make` target to fill
in the version from `Cargo.toml`. Add `.gitattributes` to prevent `git
archive` from archiving some files (should more be omitted from the
release? What about the `.cargo` directory?) and
`.github/workflows/pgxn-release.yml` to do the actual release when a tag
is pushed.

Also tweak the `README` a bit to address some inconsistencies.

.gitattributes

@@ -0,0 +1,4 @@
+.gitignore export-ignore
+.gitattributes export-ignore
+.github export-ignore
+*.bak export-ignore

.github/workflows/pgxn-release.yml

@@ -0,0 +1,21 @@
+name: ⚙️ Release on PGXN
+on:
+  push:
+    tags: [v*]
+    branches: [pgxn]
+jobs:
+  release:
+    name: Release on PGXN
+    runs-on: ubuntu-latest
+    container: pgxn/pgxn-tools
+    steps:
+    - name: Check out the repo
+      uses: actions/checkout@v4
+    - name: Bundle the Release
+      run: make META.json.bak && pgxn-bundle
+    - name: Release on PGXN
+      env:
+        PGXN_USERNAME: ${{ secrets.PGXN_USERNAME }}
+        PGXN_PASSWORD: ${{ secrets.PGXN_PASSWORD }}
+      # run: pgxn-release
+      run: ls -lah

.gitignore

@@ -9,3 +9,4 @@ docker/**
 *.deb
 poetry.lock
 site
+*.bak

META.json

@@ -0,0 +1,49 @@
+{
+   "name": "pgmq",
+   "abstract": "A lightweight message queue like AWS SQS or RSMQ, but on Postgres",
+   "description": "A lightweight message queue for PostgreSQL, like AWS SQS or RSMQ, but entirely in the database.",
+   "version": "@CARGO_VERSION@",
+   "maintainer": [
+      "Tembo <[email protected]>"
+   ],
+   "license": "postgresql",
+   "provides": {
+      "pgmq": {
+         "abstract": "A lightweight message queue like AWS SQS or RSMQ, but on Postgres",
+         "file": "src/sql_src.sql",
+         "docfile": "README.md",
+         "version": "@CARGO_VERSION@"
+      }
+   },
+   "prereqs": {
+      "runtime": {
+         "requires": {
+            "PostgreSQL": "11.0.0"
+         },
+         "recommends": {
+            "pg_partman": "4.5.1"
+         }
+      }
+   },
+   "resources": {
+      "bugtracker": {
+         "web": "https://github.com/tembo-io/pgmq/issues/"
+      },
+      "repository": {
+         "url": "git://github.com/tembo-io/pgmq.git",
+         "web": "https://github.com/tembo-io/pgmq/",
+         "type": "git"
+      }
+   },
+   "generated_by": "David E. Wheeler",
+   "meta-spec": {
+      "version": "1.0.0",
+      "url": "https://pgxn.org/meta/spec.txt"
+   },
+   "tags": [
+      "mq",
+      "message queue",
+      "sqs",
+      "rsmq"
+   ]
+}

Makefile

@@ -1,4 +1,5 @@
 PGRX_POSTGRES ?= pg15
+DISTVERSION  = $(shell grep -m 1 '^version' Cargo.toml | sed -e 's/[^"]*"\([^"]*\)",\{0,1\}/\1/')
 
 test:
 	cargo pgrx test $(PGRX_POSTGRES)
@@ -10,3 +11,10 @@ format:
 
 run.postgres:
 	docker run -d --name pgmq-pg -e POSTGRES_PASSWORD=postgres -p 5432:5432 quay.io/tembo/pgmq-pg:latest
+
+META.json.bak: Cargo.toml META.json
+	@sed -i.bak "s/@CARGO_VERSION@/$(DISTVERSION)/g" META.json
+
+pgxn-zip: META.json.bak
+	git archive --format zip --prefix=pgmq-$(DISTVERSION)/ -o pgmq-$(DISTVERSION).zip HEAD
+	@mv META.json.bak META.json

README.md

@@ -68,21 +68,20 @@ Community
 
 ## SQL Examples
 
-
 ```bash
 # Connect to Postgres
 psql postgres://postgres:[email protected]:5432/postgres
 ```
 
 ```sql
--- create the extension
+-- create the extension in the "pgmq" schema
 CREATE EXTENSION pgmq;
 ```
 
 ### Creating a queue
 
-Every queue is its own table in Postgres. The table name is the queue name prefixed with `q_`.
-For example, `q_my_queue` is the table for the queue `my_queue`.
+Every queue is its own table in the `pgmq` schema. The table name is the queue name prefixed with `q_`.
+For example, `pgmq.q_my_queue` is the table for the queue `my_queue`.
 
 ```sql
 -- creates the queue
@@ -121,11 +120,11 @@ The message id is returned from the send function.
 ### Read messages
 
 Read `2` message from the queue. Make them invisible for `30` seconds.
- If the messages are not deleted or archived within 30 seconds, they will become visible again
-    and can be read by another consumer.
+If the messages are not deleted or archived within 30 seconds, they will become visible again
+and can be read by another consumer.
 
 ```sql
-SELECT pgmq.read('my_queue', 30, 2);
+SELECT * FROM pgmq.read('my_queue', 30, 2);
 ```
 
 ```text
@@ -161,11 +160,10 @@ SELECT pgmq.pop('my_queue');
 
 ### Archive a message
 
-Archiving a message removes it from the queue, and inserts it to the archive table.
-
-Archive message with msg_id=2.
+Archiving a message removes it from the queue and inserts it to the archive table.
 
 ```sql
+-- Archive message with msg_id=2.
 SELECT pgmq.archive('my_queue', 2);
 ```
 
@@ -176,8 +174,8 @@ SELECT pgmq.archive('my_queue', 2);
 (1 row)
 ```
 
-Archive tables have the prefix `a_`:
 ```sql
+-- Archive tables have the prefix `a_`:
 SELECT * FROM pgmq.a_my_queue;
 ```