Enforces a minimum Bazel version

Signed-off-by: irbekrm <irbekrm@gmail.com>

WORKSPACE

@@ -1,6 +1,12 @@
 # gazelle:repository_macro hack/build/repos.bzl%go_repositories
 workspace(name = "com_github_jetstack_cert_manager")
 
+load("//:workspace.bzl", "check_min_bazel_version")
+
+# rules_go v0.28.0 requires Bazel v4.0.0 as minimum
+# https://github.com/bazelbuild/rules_go/releases/tag/v0.28.0
+check_min_bazel_version("4.0.0")
+
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 http_archive(

workspace.bzl

@@ -0,0 +1,42 @@
+# Copyright 2021 The cert-manager Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# File contents copied from https://github.com/pixie-io/pixie/blob/main/workspace.bzl
+
+# Common functions and imports used by the WORKSPACE file.
+
+def _parse_bazel_version(bazel_version):
+    # Remove commit from version.
+    version = bazel_version.split(" ", 1)[0]
+
+    # Split into (release, date) parts and only return the release
+    # as a tuple of integers.
+    parts = version.split("-", 1)
+
+    # Turn "release" into a tuple of strings
+    version_tuple = ()
+    for number in parts[0].split("."):
+        version_tuple += (str(number),)
+    return version_tuple
+
+# Check that a minimum version of bazel is being used.
+def check_min_bazel_version(bazel_version):
+    if "bazel_version" in dir(native) and native.bazel_version:
+        current_bazel_version = _parse_bazel_version(native.bazel_version)
+        minimum_bazel_version = _parse_bazel_version(bazel_version)
+        if minimum_bazel_version > current_bazel_version:
+            fail("\nCurrent Bazel version is {}, expected at least {}\n".format(
+                native.bazel_version,
+                bazel_version,
+            ))