Add a pre-commit sample-config command

tests/commands/sample_config_test.py

@@ -0,0 +1,21 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+from pre_commit.commands.sample_config import sample_config
+
+
+def test_sample_config(capsys):
+    ret = sample_config()
+    assert ret == 0
+    out, _ = capsys.readouterr()
+    assert out == '''\
+# See http://pre-commit.com for more information
+# See http://pre-commit.com/hooks.html for more hooks
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    sha: v0.7.1
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: check-yaml
+    -   id: check-added-large-files
+'''