Initial commit (docker/build-push-action#87)

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

README.md

@@ -0,0 +1,118 @@
+## About
+
+GitHub Action to set up Docker [Buildx](https://github.com/docker/buildx).
+
+___
+
+* [Usage](#usage)
+  * [Quick start](#quick-start)
+  * [With QEMU](#with-qemu)
+* [Customizing](#customizing)
+  * [inputs](#inputs)
+  * [outputs](#outputs)
+  * [environment variables](#environment-variables)
+* [Limitation](#limitation)
+
+## Usage
+
+### Quick start
+
+```yaml
+name: ci
+
+on:
+  push:
+
+jobs:
+  buildx:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v2
+      -
+        name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+        with:
+          version: latest
+      -
+        name: Builder instance name
+        run: echo ${{ steps.buildx.outputs.name }}
+      -
+        name: Available platforms
+        run: echo ${{ steps.buildx.outputs.platforms }}
+```
+
+### With QEMU
+
+If you want support for more platforms you can use our [setup-qemu](https://github.com/docker/setup-qemu-action) action:
+
+```yaml
+name: ci
+
+on:
+  pull_request:
+    branches: master
+  push:
+    branches: master
+    tags:
+
+jobs:
+  buildx:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v2
+      -
+        name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+        with:
+          platforms: all
+      -
+        name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+        with:
+          version: latest
+      -
+        name: Available platforms
+        run: echo ${{ steps.buildx.outputs.platforms }}
+```
+
+## Customizing
+
+### inputs
+
+Following inputs can be used as `step.with` keys
+
+| Name               | Type    | Default                           | Description                        |
+|--------------------|---------|-----------------------------------|------------------------------------|
+| `version`          | String  | _the one installed on the runner_ | [Buildx](https://github.com/docker/buildx) version. e.g. `v0.3.0`, `latest` |
+| `driver`           | String  | `docker-container`                | Sets the [builder driver](https://github.com/docker/buildx#--driver-driver) to be used. |
+| `driver-opt`       | String  |                                   | Passes additional [driver-specific options](https://github.com/docker/buildx#--driver-opt-options). e.g. `image=moby/buildkit:master` |
+| `buildkitd-flags`  | String  |                                   | [Flags for buildkitd](https://github.com/moby/buildkit/blob/master/docs/buildkitd.toml.md) daemon. |
+| `install`          | Bool    | `false`                           | Sets up `docker build` command as an alias to `docker buildx` |
+| `use`              | Bool    | `true`                            | Switch to this builder instance |
+
+### outputs
+
+Following outputs are available
+
+| Name          | Type    | Description                           |
+|---------------|---------|---------------------------------------|
+| `name`        | String  | Builder instance name |
+| `platforms`   | String  | Available platforms (comma separated) |
+
+### environment variables
+
+The following [official docker environment variables](https://docs.docker.com/engine/reference/commandline/cli/#environment-variables) are supported:
+
+| Name            | Type    | Default      | Description                                    |
+|-----------------|---------|-------------|-------------------------------------------------|
+| `DOCKER_CONFIG` | String  | `~/.docker` | The location of your client configuration files |
+
+## Limitation
+
+This action is only available for Linux [virtual environments](https://help.github.com/en/articles/virtual-environments-for-github-actions#supported-virtual-environments-and-hardware-resources).