Documentation for Just, closes #494

Also added 'just init' and fixed a couple of missing pipenv run calls.

Justfile

@@ -1,6 +1,10 @@
 # Run tests and linters
 @default: test lint
 
+# Setup project
+@init:
+  pipenv run pip install -e '.[test,docs,mypy,flake8]'
+
 # Run pytest with supplied options
 @test *options:
   pipenv run pytest {{options}}
@@ -10,11 +14,11 @@
   pipenv run black . --check
   pipenv run flake8
   pipenv run mypy sqlite_utils tests
-  cog --check README.md docs/*.rst
+  pipenv run cog --check README.md docs/*.rst
 
 # Rebuild docs with cog
 @cog:
-  cog -r README.md docs/*.rst
+  pipenv run cog -r README.md docs/*.rst
 
 @docs: cog
   cd docs && pipenv run make livehtml

docs/contributing.rst

@@ -79,6 +79,46 @@ Both commands can then be run in the root of the project like this::
 
 All three of these tools are run by our CI mechanism against every commit and pull request.
 
+Using Just and pipenv
+=====================
+
+If you install `Just <https://github.com/casey/just>`__ and `pipenv <https://pipenv.pypa.io/>`__ you can use them to manage your local development environment.
+
+To create a virtual environment and install all development dependencies, run::
+
+    cd sqlite-utils
+    just init
+
+To run all of the tests and linters::
+
+    just
+
+To run tests, or run a specific test module or test by name::
+
+    just test # All tests
+    just test tests/test_cli_memory.py # Just this module
+    just test -k test_memory_no_detect_types # Just this test
+
+To run just the linters::
+
+    just lint
+
+To apply Black to your code::
+
+    just black
+
+To update documentation using Cog::
+
+    just cog
+
+To run the live documentation server (after building with Cog first)::
+
+    just docs
+
+And to list all available commands::
+
+    just -l
+
 .. _release_process:
 
 Release process