Add sql-lint: style linter for PostgreSQL SQL files

.github/workflows/ci.yml

@@ -9,7 +9,32 @@ on:
     branches: [master]
   pull_request:
 jobs:
+  # Style linter (https://github.com/Postgres-Extensions/linter, vendored at
+  # .vendor/linter). Deliberately checked out WITHOUT submodules -- `make
+  # lint` is the same command a developer runs locally, and lint.mk
+  # self-initializes the submodule on first use (see its comment). Using the
+  # exact same entry point here is what actually proves that self-init works,
+  # rather than papering over it with a submodules: true checkout. The
+  # linter's own test suite (fixtures + scanner edge cases) is that repo's
+  # own CI's job, not this one's. No PostgreSQL needed -- sql-lint is a
+  # standalone Perl script -- so this doesn't use the pgxn-tools container.
+  lint:
+    name: 🧹 SQL Lint
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v5
+      - name: Lint SQL
+        run: make lint
+
   test:
+    # Gated behind lint: the 12-leg PG matrix below is comparatively
+    # expensive, and every leg would fail anyway on a baseline that's already
+    # broken by a lint violation. success() is required explicitly once a
+    # job's `if:` references anything -- GitHub only assumes success() as a
+    # default when no `if:` is written at all.
+    needs: [lint]
+    if: success()
     strategy:
       matrix:
         pg: [17, 16, 15, 14, 13, 12, 11, 10, 9.6, 9.5, 9.4, 9.3]
@@ -30,7 +55,7 @@ jobs:
   # job succeeded or was skipped (e.g. a docs-only push with paths-ignore) and
   # fails if any failed or were cancelled.
   all-checks-passed:
-    needs: [test]
+    needs: [lint, test]
     if: always()
     runs-on: ubuntu-latest
     steps:

.gitmodules

@@ -0,0 +1,3 @@
+[submodule ".vendor/linter"]
+	path = .vendor/linter
+	url = https://github.com/Postgres-Extensions/linter

Makefile

@@ -15,3 +15,14 @@ install: deps
 cat_tools: $(DESTDIR)$(datadir)/extension/cat_tools.control
 $(DESTDIR)$(datadir)/extension/cat_tools.control:
 	pgxn install 'cat_tools>=0.2.1' --sudo
+
+# Style linter (see https://github.com/Postgres-Extensions/linter, vendored
+# at .vendor/linter -- lint.mk is the thin local hand-off, see its comment).
+# Scoped to the actively-maintained source rather than the default
+# `sql/ test/`: sql/extension_drop--1.0.0.sql is a frozen, already-released
+# version file (RELEASE.md's "Ongoing development" section -- once a version
+# is released, its sql/<ext>--<version>.sql is never hand-edited again), so
+# linting it would produce permanent, unfixable findings and make `make
+# lint` unusable as a CI gate. Lint the hand-maintained source instead.
+LINT_TARGETS = sql/extension_drop.sql test/
+include lint.mk

lint.mk

@@ -0,0 +1,26 @@
+# lint.mk — thin wrapper; the whole local footprint for consuming
+# https://github.com/Postgres-Extensions/linter. Everything else lives in
+# the .vendor/linter submodule; see its README for available targets/rules.
+#
+# Self-initializing (via the rule below) so `make lint` works right after a
+# plain `git clone`, with no --recurse-submodules needed, and so CI can rely
+# on the exact same entry point a developer would use locally.
+#
+# Guarded on a real .git being present (directory for a normal clone, or a
+# `gitdir:` file for a worktree/submodule checkout -- $(wildcard .git) matches
+# both). A source tarball (git archive output -- PGXN dist packages, `make
+# dist`) has no .git at all and never contains submodule content, so without
+# this guard GNU Make would still try to satisfy the `include` below via the
+# remake rule on every invocation, `git submodule update --init` would fail
+# immediately ("fatal: not a git repository"), and that failure would abort
+# every `make` target -- not just `make lint` -- in a tarball build. Lint
+# simply isn't available/attempted outside a real git checkout, which is
+# correct: a tarball build has no reason to lint.
+ifneq ($(wildcard .git),)
+
+.vendor/linter/lint.mk:
+	git submodule update --init -- .vendor/linter
+
+include .vendor/linter/lint.mk
+
+endif