Add pre-commit to review syntax with Black

References:
* casework/CASE-Utilities-Python#37
* https://github.com/psf/black/blob/main/docs/integrations/source_version_control.md

Signed-off-by: Alex Nelson <[email protected]>

Author: ajnelson-nist

.gitignore

@@ -5,6 +5,7 @@
 *.svg
 *.swp
 .DS_Store
+.venv-pre-commit
 _*
 build
 dist

.pre-commit-config.yaml

@@ -0,0 +1,16 @@
+# This software was developed at the National Institute of Standards
+# and Technology by employees of the Federal Government in the course
+# of their official duties. Pursuant to title 17 Section 105 of the
+# United States Code this software is not subject to copyright
+# protection and is in the public domain. NIST assumes no
+# responsibility whatsoever for its use by other parties, and makes
+# no guarantees, expressed or implied, about its quality,
+# reliability, or any other characteristic.
+#
+# We would appreciate acknowledgement if the software is used.
+
+repos:
+  - repo: https://github.com/psf/black
+    rev: 22.3.0
+    hooks:
+      - id: black

Makefile

@@ -16,7 +16,8 @@ SHELL := /bin/bash
 PYTHON3 ?= python3
 
 all: \
-  .git_submodule_init.done.log
+  .git_submodule_init.done.log \
+  .venv-pre-commit/var/.pre-commit-built.log
 	$(MAKE) \
 	  PYTHON3=$(PYTHON3) \
 	  --directory tests
@@ -37,8 +38,32 @@ all: \
 	  .git_submodule_init.done.log
 	touch $@
 
+# This virtual environment is meant to be built once and then persist, even through 'make clean'.
+# If a recipe is written to remove this flag file, it should first run `pre-commit uninstall`.
+.venv-pre-commit/var/.pre-commit-built.log:
+	rm -rf .venv-pre-commit
+	test -r .pre-commit-config.yaml \
+	  || (echo "ERROR:Makefile:pre-commit is expected to install for this repository, but .pre-commit-config.yaml does not expect to exist." >&2 ; exit 1)
+	$(PYTHON3) -m venv \
+	  .venv-pre-commit
+	source .venv-pre-commit/bin/activate \
+	  && pip install \
+	    --upgrade \
+	    pip \
+	    setuptools \
+	    wheel
+	source .venv-pre-commit/bin/activate \
+	  && pip install \
+	    pre-commit
+	source .venv-pre-commit/bin/activate \
+	  && pre-commit install
+	mkdir -p \
+	  .venv-pre-commit/var
+	touch $@
+
 check: \
-  .git_submodule_init.done.log
+  .git_submodule_init.done.log \
+  .venv-pre-commit/var/.pre-commit-built.log
 	$(MAKE) \
 	  PYTHON3=$(PYTHON3) \
 	  --directory tests \