feat!: drop support for bazel 6 (#345)

Author: p0deje

.bcr/presubmit.yml

@@ -2,7 +2,7 @@
 bcr_test_module:
   module_path: "examples/gem"
   matrix:
-    bazel: ["8.x", "7.x", "6.x"]
+    bazel: ["8.x", "7.x"]
     # NB: Windows is removed due to https://github.com/bazel-contrib/rules_ruby/issues/64
     platform: ["debian10", "macos", "ubuntu2004"]
   tasks:

.github/workflows/release_prep.sh

@@ -23,45 +23,11 @@ tar --create --auto-compress \
 
 # The stdout of this program will be used as the top of the release notes for this release.
 cat << EOF
-## Using Bzlmod with Bazel 7-8
+## Using Bzlmod
 
 1. Add to your \`MODULE.bazel\` file:
 
 \`\`\`starlark
 bazel_dep(name = "rules_ruby", version = "${TAG:1}")
 \`\`\`
-
-## Using Bzlmod with Bazel 6
-
-1. Enable with \`common --enable_bzlmod\` in \`.bazelrc\`.
-2. Add to your \`MODULE.bazel\` file:
-
-\`\`\`starlark
-bazel_dep(name = "rules_ruby", version = "${TAG:1}")
-\`\`\`
-
-## Using WORKSPACE
-
-Paste this snippet into your \`WORKSPACE.bazel\` file:
-
-\`\`\`starlark
-load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
-
-# Skylib is a dependency, remove if you already have it.
-http_archive(
-    name = "bazel_skylib",
-    sha256 = "74d544d96f4a5bb630d465ca8bbcfe231e3594e5aae57e1edbf17a6eb3ca2506",
-    urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.3.0/bazel-skylib-1.3.0.tar.gz",
-        "https://github.com/bazelbuild/bazel-skylib/releases/download/1.3.0/bazel-skylib-1.3.0.tar.gz",
-    ],
-)
-
-http_archive(
-    name = "rules_ruby",
-    sha256 = "${SHA}",
-    strip_prefix = "${PREFIX}",
-    url = "https://github.com/bazel-contrib/rules_ruby/releases/download/${TAG}/${ARCHIVE}",
-)
-\`\`\`
 EOF

README.md

@@ -8,7 +8,6 @@ The ruleset is known to work with:
 
 - Bazel 8 using WORKSPACE and Bzlmod _(tested on CI)_.
 - Bazel 7 using WORKSPACE and Bzlmod _(no longer tested on CI)_.
-- Bazel 6 using WORKSPACE and Bzlmod _(no longer tested on CI)_.
 
 ## Getting Started