Docker hook support for pre-commit

pre_commit/languages/all.py

@@ -1,5 +1,6 @@
 from __future__ import unicode_literals
 
+from pre_commit.languages import docker
 from pre_commit.languages import node
 from pre_commit.languages import pcre
 from pre_commit.languages import python
@@ -40,6 +41,7 @@ from pre_commit.languages import system
 #     """
 
 languages = {
+    'docker': docker,
     'node': node,
     'pcre': pcre,
     'python': python,

pre_commit/languages/docker.py

@@ -0,0 +1,62 @@
+from __future__ import unicode_literals
+
+import hashlib
+import os
+
+from pre_commit.languages import helpers
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import mkdirp
+from pre_commit.xargs import xargs
+
+
+ENVIRONMENT_DIR = 'docker'
+
+
+def md5(s):
+    m = hashlib.md5()
+    m.update(s)
+    return m.hexdigest()
+
+
+def docker_tag(repo_cmd_runner):
+    return 'pre-commit-{}'.format(
+        md5(os.path.basename(repo_cmd_runner.path()))
+    ).lower()
+
+
+def install_environment(
+        repo_cmd_runner,
+        version='default',
+        additional_dependencies=(),
+):
+    assert repo_cmd_runner.exists('Dockerfile')
+    # I don't know of anybody trying to juggle multiple docker installations
+    # so this seems sufficient
+    directory = helpers.environment_dir(ENVIRONMENT_DIR, 'default')
+    mkdirp(os.path.join(repo_cmd_runner.path(), directory))
+
+    cmd = (
+        'docker', 'build', '--pull',
+        '--tag', docker_tag(repo_cmd_runner),
+        '.'
+    )
+
+    # Docker doesn't really have relevant disk environment, but pre-commit
+    # still needs to cleanup it's state files on failure
+    env_dir = repo_cmd_runner.path(directory)
+    with clean_path_on_failure(env_dir):
+        helpers.run_setup_cmd(repo_cmd_runner, cmd)
+
+
+def run_hook(repo_cmd_runner, hook, file_args):
+    cmd = (
+        'docker', 'run',
+        '-t',
+        '-v', '{}:/src'.format(os.getcwd()),
+        '--workdir', '/src',
+        docker_tag(repo_cmd_runner)
+    )
+
+    return xargs(
+        cmd + (hook['entry'],) + tuple(hook['args']), file_args,
+    )