chore: add pre-commit hook (#60)

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Source-Link: googleapis/synthtool@aa255b1
Source-Link: googleapis/synthtool@f943185
Source-Link: googleapis/synthtool@69629b6
Source-Link: googleapis/synthtool@32af6da

.pre-commit-config.yaml

@@ -0,0 +1,17 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.4.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: check-yaml
+-   repo: https://github.com/psf/black
+    rev: 19.10b0
+    hooks:
+    - id: black
+-   repo: https://gitlab.com/pycqa/flake8
+    rev: 3.8.4
+    hooks:
+    - id: flake8

CONTRIBUTING.rst

@@ -111,6 +111,16 @@ Coding Style
   should point to the official ``googleapis`` checkout and the
   the branch should be the main branch on that remote (``master``).
 
+- This repository contains configuration for the
+  `pre-commit <https://pre-commit.com/>`__ tool, which automates checking
+  our linters during a commit.  If you have it installed on your ``$PATH``,
+  you can enable enforcing those checks via:
+
+.. code-block:: bash
+
+   $ pre-commit install
+   pre-commit installed at .git/hooks/pre-commit
+
 Exceptions to PEP8:
 
 - Many unit tests use a helper method, ``_call_fut`` ("FUT" is short for

noxfile.py

@@ -81,9 +81,8 @@ def default(session):
     session.run(
         "py.test",
         "--quiet",
-        "--cov=google.cloud.recommender",
-        "--cov=google.cloud",
-        "--cov=tests.unit",
+        "--cov=google/cloud",
+        "--cov=tests/unit",
         "--cov-append",
         "--cov-config=.coveragerc",
         "--cov-report=",

synth.metadata

@@ -19,14 +19,14 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "68742c6016bf0d16948a572633d17955a8737414"
+        "sha": "aa255b15d52b6d8950cca48cfdf58f7d27a60c8a"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "68742c6016bf0d16948a572633d17955a8737414"
+        "sha": "aa255b15d52b6d8950cca48cfdf58f7d27a60c8a"
       }
     }
   ],
@@ -94,6 +94,7 @@
     ".kokoro/test-samples.sh",
     ".kokoro/trampoline.sh",
     ".kokoro/trampoline_v2.sh",
+    ".pre-commit-config.yaml",
     ".trampolinerc",
     "CODE_OF_CONDUCT.md",
     "CONTRIBUTING.rst",