Pre-commit hook for style checks and other normalizations

Activated checks
- trailing-whitespace
- end-of-file-fixer
- check-yaml
- check-added-large-files
- flake8
- black

Flake8 is configured to ignore issues E501, F403, and F401 for now. They will be
fixed later.

Also added some lines about HACKING to README.md, describing the setup of the
environment including these developer tools.

.pre-commit-config.yaml

@@ -0,0 +1,15 @@
+# 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: v2.0.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: check-yaml
+    -   id: check-added-large-files
+    -   id: flake8
+-   repo: https://github.com/psf/black
+    rev: 19.3b0
+    hooks:
+    -   id: black

README.md

@@ -51,7 +51,8 @@ Requirements
 
 HeAT is based on [PyTorch](https://pytorch.org/). Specifially, we are exploiting
 PyTorch's support for GPUs *and* MPI parallelism. For MPI support we utilize
-[mpi4py](https://mpi4py.readthedocs.io). Both packages can be installed via pip or automatically using the setup.py.
+[mpi4py](https://mpi4py.readthedocs.io). Both packages can be installed via pip
+or automatically using the setup.py.
 
 
 Installation
@@ -66,13 +67,28 @@ install the latest version with
 where the part in brackets is a list of optional dependencies. You can omit
 it, if you do not need HDF5 or NetCDF support.
 
+Hacking
+-------
+
 If you want to work with the development version, you can checkout the sources using
 
 > $ git clone https://github.com/helmholtz-analytics/heat.git
 
 The installation can then be done from the checked out sources with
 
-> $ pip install .[hdf5, netcdf]
+> $ pip install .[hdf5, netcdf, dev]
+
+The extra `dev` dependency pulls in additional tools to support the enforcement
+of coding conventions ([Black](https://github.com/psf/black)) and to support a
+pre-commit hook to do the same. In order to fully use this framework, please
+also install the pre-commit hook with
+
+> $ pre-commit install
+
+In order to check compliance of your changes before even trying to commit anything,
+you can runs
+
+> $ pre-commit run --all-files
 
 License
 -------

setup.cfg

@@ -7,4 +7,4 @@ ignore = E203,E402,W503
 
 [flake8]
 max-line-length = 88
-ignore = E203,E402,W503
+ignore = E203,E402,W503,E501,F403,F401