Merge baac374 into fe24a15

README.md

@@ -35,6 +35,7 @@ Try it out now using the [Black Playground](https://black.now.sh).
 **[Code style](#the-black-code-style)** |
 **[pyproject.toml](#pyprojecttoml)** |
 **[Editor integration](#editor-integration)** |
+**[Docker image](#docker-image)** |
 **[blackd](#blackd)** |
 **[Version control integration](#version-control-integration)** |
 **[Ignoring unmodified files](#ignoring-unmodified-files)** |
@@ -280,7 +281,7 @@ ignore = E501
 ```
 
 You'll find *Black*'s own .flake8 config file is configured like this.
-If you're curious about the reasoning behind B950, 
+If you're curious about the reasoning behind B950,
 [Bugbear's documentation](https://github.com/PyCQA/flake8-bugbear#opinionated-warnings)
 explains it.  The tl;dr is "it's like highway speed limits, we won't
 bother you if you overdo it by a few km/h".
@@ -759,6 +760,32 @@ affect your use case.
 
 This can be used for example with PyCharm's [File Watchers](https://www.jetbrains.com/help/pycharm/file-watchers.html).
 
+## Docker image
+
+### Building
+
+Running `build.sh` in the `docker/` folder will build the docker image tagged as `ambv/black:latest`
+
+### Tagging
+
+Running `tag.sh` in the `docker/` folder will tag the `ambv/black:latest` image based on the `__version__` in `black.py`
+
+### Usage
+
+`docker run ambv/black` defaults to the `--help` flag.
+
+To run a check on a python file:
+
+```bash
+docker run --read-only  -v $(pwd):$(pwd) -w $(pwd) ambv/black --check foo.py
+```
+
+Note that the mounted directory has to be where the file exists, e.g.,
+
+```bash
+docker run --read-only  -v /home/ubunu/somefolder/:/black/ -w /black/ ambv/black --check foo.py
+```
+
 ## blackd
 
 `blackd` is a small HTTP server that exposes *Black*'s functionality over

docker/Dockerfile

@@ -0,0 +1,13 @@
+FROM alpine:3.6
+
+RUN apk add --no-cache --update python3 \
+      && apk add --no-cache --virtual .build-deps py-pip \
+      && pip3 --no-cache-dir install black \
+      && apk del --no-cache --purge .build-deps \
+      && rm -rf /usr/lib/python2.* \
+      && rm -rf /var/cache/* \
+      && rm -rf /root/.cache/* \
+      && find /usr/lib/python* -depth \( -name '*.pyo' -o -name '*.pyc' -o -name 'test' -o -name 'tests' \) -exec rm -rf '{}' + ;
+
+ENTRYPOINT ["/usr/bin/black" ]
+CMD ["--help"]

docker/build.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+BASEDIR=$(dirname "$0")
+VERSION="latest"
+IMAGENAME="ambv/black"
+
+docker build -t ${IMAGENAME}:"${VERSION}" -f "${BASEDIR}"/Dockerfile "${BASEDIR}"

docker/tag.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+BASEDIR=$(dirname "$0")
+VERSION="latest"
+IMAGENAME="ambv/black"
+
+if [ -n "$(docker images -q "${IMAGENAME}:${VERSION}" 2> /dev/null)" ]; then
+  TAG="$(grep -iR "^__version__ =" "${BASEDIR}"/../black.py | awk -F "= " '{print $2}' | sed 's/"//g')"
+  docker tag "${IMAGENAME}:${VERSION}" "${IMAGENAME}:${TAG}"
+  echo "tagged image ${IMAGENAME}:${TAG}"
+fi