Add pre-commit hook following icefall convention (#72)

* Add pre-commit hook following icefall convention

* Add style check CI from icefall

* Add python style check

.github/workflows/python_style_check.yml

@@ -0,0 +1,64 @@
+# Copyright      2021  Fangjun Kuang (csukuangfj@gmail.com)
+
+# See ../../LICENSE for clarification regarding multiple authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: python_style_check
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  style_check:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-18.04, macos-10.15]
+        python-version: [3.7, 3.9]
+      fail-fast: false
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Setup Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v1
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install Python dependencies
+        run: |
+          python3 -m pip install --upgrade pip black==21.6b0 flake8==3.9.2 click==8.0.4
+          # See https://github.com/psf/black/issues/2964
+          # The version of click should be selected from 8.0.0, 8.0.1, 8.0.2, 8.0.3, and 8.0.4
+
+      - name: Run flake8
+        shell: bash
+        working-directory: ${{github.workspace}}
+        run: |
+          # stop the build if there are Python syntax errors or undefined names
+          flake8 . --count --show-source --statistics
+          flake8 .
+
+      - name: Run black
+        shell: bash
+        working-directory: ${{github.workspace}}
+        run: |
+          black --check --diff .

.pre-commit-config.yaml

@@ -0,0 +1,28 @@
+repos:
+  - repo: https://github.com/psf/black
+    rev: 21.6b0
+    hooks:
+      - id: black
+        args: [--line-length=80]
+        additional_dependencies: ['click==8.0.1']
+        exclude: icefall\/__init__\.py
+
+  - repo: https://github.com/PyCQA/flake8
+    rev: 3.9.2
+    hooks:
+      - id: flake8
+        args: [--max-line-length=80]
+
+  - repo: https://github.com/pycqa/isort
+    rev: 5.9.2
+    hooks:
+      - id: isort
+        args: [--profile=black, --line-length=80]
+
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.0.1
+    hooks:
+      - id: check-executables-have-shebangs
+      - id: end-of-file-fixer
+      - id: mixed-line-ending
+      - id: trailing-whitespace

README.md

@@ -325,3 +325,30 @@ Errors: 112 insertions, 93 deletions, 876 substitutions, over 52576 reference wo
 If you have a GPU with a larger RAM (e.g., 32 GB), you can get an even **lower** RTF.
 
 [icefall]: https://github.com/k2-fsa/icefall/
+
+
+### Contributing
+
+Contributions to ```sherpa``` are very welcomed. There are many possible ways to make contributions 
+and two of them are:
+- To write documentation
+- To write code:
+  - To follow the code style in the repository
+  - To write a new features (support new architectures, new beam search, etc)
+
+### Follow the code style
+
+We use the following tools to make the code style to be as consistent as possible:
+
+  - [black](https://github.com/psf/black), to format the code
+  - [flake8](https://github.com/PyCQA/flake8), to check the style and quality of the code
+  - [isort](https://github.com/PyCQA/isort), to sort ``imports``
+
+After running the following commands:
+
+    $ git clone https://github.com/k2-fsa/sherpa
+    $ cd sherpa
+    $ pip install pre-commit
+    $ pre-commit install
+
+it will run the checks whenever you run ``git commit`` **automatically**