go.mk: remove submodule and initialize through make

.github/workflows/main.yml

@@ -19,5 +19,5 @@ jobs:
         go-version: '^1.18'
     - name: Lint code
       run: |
-        git submodule update --init --recursive go.mk
+        make go.mk
         PATH=$(go env GOPATH)/bin:$PATH make lint

.github/workflows/release.yml

@@ -18,7 +18,7 @@ jobs:
         with:
           fetch-depth: 0
 
-      - run: git submodule update --init --recursive go.mk
+      - run: make go.mk
         shell: bash
 
       - name: Import GPG key

.gitignore

@@ -20,3 +20,4 @@ _test
 dist
 release
 bin
+/go.mk

Makefile

@@ -1,5 +1,36 @@
+GO_MK_REF := v1.0.0
+
+# make go.mk a dependency for all targets
+.EXTRA_PREREQS = go.mk
+
+ifndef MAKE_RESTARTS
+# This section will be processed the first time that make reads this file.
+
+# This causes make to re-read the Makefile and all included
+# makefiles after go.mk has been cloned.
+Makefile:
+	@touch Makefile
+endif
+
+.PHONY: go.mk
+.ONESHELL:
+go.mk:
+	@if [ ! -d "go.mk" ]; then
+		git clone https://github.com/exoscale/go.mk.git
+	fi
+	@cd go.mk
+	@if ! git show-ref --quiet --verify "refs/heads/${GO_MK_REF}"; then
+		git fetch
+	fi
+	@if ! git show-ref --quiet --verify "refs/tags/${GO_MK_REF}"; then
+		git fetch --tags
+	fi
+	git checkout --quiet ${GO_MK_REF}
+
 PROJECT_URL = https://github.com/exoscale/cert-manager-webhook-exoscale
+go.mk/init.mk:
 include go.mk/init.mk
+go.mk/public.mk:
 include go.mk/public.mk
 
 GO ?= $(shell which go)