Adds codespaces support, closes HypothesisWorks#2735 (HypothesisWorks#2880)

Author: sobolevn

.devcontainer/devcontainer.json

@@ -0,0 +1,12 @@
+{ 
+  "name": "HypothesisWorks/hypothesis",
+  "image": "python:3.8-slim-buster",
+
+  "settings": {
+    "python.pythonPath": "${workspaceFolder}/.venv/bin/python3",
+  },
+
+  // After container is created, we install all the requirements,
+  // and show what commands there are in our own tooling:
+  "postCreateCommand": "apt-get update && apt-get install -y make shellcheck && make check-installed",
+}

.gitignore

@@ -32,6 +32,7 @@ htmlcov
 build
 dist
 .doctrees/
+.venv/
 
 # encrypted files
 secrets.tar

CONTRIBUTING.rst

@@ -61,6 +61,16 @@ You may wish to do all of this in a
 Will create an isolated environment where you can install and try out
 Hypothesis without affecting your system packages.
 
+----------
+Codespaces
+----------
+
+We support `GitHub Codespaces <https://github.com/features/codespaces>`_.
+It really helps us to make the contribution process easier.
+
+It is pre-configured to install all the requirements for you.
+The only thing left for a contributor is to press "Open with Codespaces" button.
+
 -----------------------
 Copyright and Licensing
 -----------------------

build.sh

@@ -17,8 +17,8 @@ SCRIPTS="$ROOT/tooling/scripts"
 # shellcheck source=tooling/scripts/common.sh
 source "$SCRIPTS/common.sh"
 
-if [ -n "${GITHUB_ACTIONS-}" ] ; then
-    # We're on GitHub Actions and already set up a suitable Python
+if [ -n "${GITHUB_ACTIONS-}" ] || [ -n "${CODESPACES-}" ] ; then
+    # We're on GitHub Actions or Codespaces and already set up a suitable Python
     PYTHON=$(command -v python)
 else
     # Otherwise, we install it from scratch