Add gazelle plugin to CI and distribution mechanism (#424)

After #400, the gazelle plugin has been cleanly separated out into its own bazel workspace, which will soon finally allow us to mark it stable. But this means:

* we need to change our bazelci config to explicitly build and test it, since `bazel build //...` no longer includes the plugin;
* we need to add proper distribution rules for it;
* we need to update release instructions, since now we will have two distribution tarballs

1 files changed, 33 insertions, 11 deletions

diff --git a/distribution/BUILD b/distribution/BUILD
index 326cee7..8762525 100644
--- a/distribution/BUILD
+++ b/distribution/BUILD
@@ -1,6 +1,6 @@
 load("@bazel_skylib//:version.bzl", "version")
 load("@rules_pkg//:pkg.bzl", "pkg_tar")
-load("@rules_pkg//releasing:defs.bzl", "print_rel_notes")
+load("@rules_pkg//:mappings.bzl", "pkg_files", "strip_prefix")
 
 package(
     default_visibility = ["//visibility:private"],
@@ -13,25 +13,47 @@ genrule(
     cmd = "sed -e '/### INTERNAL ONLY/,$$d' $(location //:MODULE.bazel) >$@",
 )
 
-# Build the artifact to put on the github release page.
+# Build the artifacts to put on the github release page.
 pkg_tar(
-    name = "bazel-skylib-%s" % version,
+    name = "bazel-skylib",
     srcs = [
         "distro_module_bazel",
         "//:distribution",
     ],
+    out = "bazel-skylib-%s.tar.gz" % version,
     extension = "tar.gz",
     mode = "0644",
     # Make it owned by root so it does not have the uid of the CI robot.
     owner = "0.0",
-    strip_prefix = ".",
+    strip_prefix = strip_prefix.from_root(),
 )
 
-print_rel_notes(
-    name = "relnotes",
-    outs = ["relnotes.txt"],
-    deps_method = "bazel_skylib_workspace",
-    repo = "bazel-skylib",
-    setup_file = ":workspace.bzl",
-    version = version,
+pkg_files(
+    name = "bazel-skylib-gazelle-plugin-without-external-prefix",
+    srcs = [
+        "@bazel_skylib_gazelle_plugin//:distribution",
+        "@bazel_skylib_gazelle_plugin//bzl:distribution",
+    ],
+    strip_prefix = strip_prefix.from_root(),
+)
+
+pkg_tar(
+    name = "bazel-skylib-gazelle-plugin",
+    srcs = [
+        ":bazel-skylib-gazelle-plugin-without-external-prefix",
+        "//:LICENSE",
+    ],
+    out = "bazel-skylib-gazelle-plugin-%s.tar.gz" % version,
+    extension = "tar.gz",
+    mode = "0644",
+    # Make it owned by root so it does not have the uid of the CI robot.
+    owner = "0.0",
+)
+
+filegroup(
+    name = "distribution",
+    srcs = [
+        "bazel-skylib",
+        "bazel-skylib-gazelle-plugin",
+    ],
 )