Enhance documentation

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

docs/advanced/cache.md

@@ -0,0 +1,107 @@
+# Cache
+
+* [Registry cache](#registry-cache)
+* [GitHub cache](#github-cache)
+
+> More info about buildx cache: https://github.com/docker/buildx#--cache-fromnametypetypekeyvalue
+
+## Registry cache
+
+You can import/export cache from a cache manifest or (special) image configuration on the registry.
+
+```yaml
+name: ci
+
+on:
+  push:
+    branches:
+      - 'master'
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v2
+      -
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      -
+        name: Login to DockerHub
+        uses: docker/login-action@v1 
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      -
+        name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: true
+          tags: user/app:latest
+          cache-from: type=registry,ref=user/app:latest
+          cache-to: type=inline
+```
+
+## GitHub cache
+
+> :warning: At the moment caches are copied over the existing cache so it [keeps growing](https://github.com/docker/build-push-action/issues/252).
+> The `Move cache` step is used as a temporary fix (see https://github.com/moby/buildkit/issues/1896).
+
+> :rocket: There is a new cache backend using GitHub cache being developed that will lighten your workflow.
+> More info: https://github.com/docker/buildx/pull/535
+
+You can leverage [GitHub cache](https://docs.github.com/en/actions/configuring-and-managing-workflows/caching-dependencies-to-speed-up-workflows)
+using [actions/cache](https://github.com/actions/cache) with this action:
+
+```yaml
+name: ci
+
+on:
+  push:
+    branches:
+      - 'master'
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v2
+      -
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      -
+        name: Cache Docker layers
+        uses: actions/cache@v2
+        with:
+          path: /tmp/.buildx-cache
+          key: ${{ runner.os }}-buildx-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-buildx-
+      -
+        name: Login to DockerHub
+        uses: docker/login-action@v1 
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      -
+        name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: true
+          tags: user/app:latest
+          cache-from: type=local,src=/tmp/.buildx-cache
+          cache-to: type=local,dest=/tmp/.buildx-cache-new
+      -
+        # Temp fix
+        # https://github.com/docker/build-push-action/issues/252
+        # https://github.com/moby/buildkit/issues/1896
+        name: Move cache
+        run: |
+          rm -rf /tmp/.buildx-cache
+          mv /tmp/.buildx-cache-new /tmp/.buildx-cache
+```