make the mac development installation instructions executable

This commit was sponsored by Jason Mills, VM (Vicky) Brasseur, Greg
Back, and my other patrons.  If you want to join them, you can support
my work at https://glyph.im/patrons/.

Author: glyph

README.md

@@ -75,8 +75,8 @@ to find something simple to contribute!  In order to run it, make sure you have
 Xcode installed (like [actual, for-real
 Xcode](https://apps.apple.com/us/app/xcode/id497799835?mt=12), not the
 command-line tools; this is a GUI, not a command-line thing, so you need the
-GUI development tools) make a virtualenv, `pip install -Ur requirements.txt`,
-and then run `./runme`.
+GUI development tools) make a virtualenv however you prefer to do that, run
+`./mac-dev-install`, and then run `./runme`.
 
 Note that if you really want to keep using the app, `./testme` creates a
 different test bundle so you can run through some quick, fake test pomodoros

mac-dev-install

@@ -0,0 +1,13 @@
+#!/bin/bash -ex
+
+if [ -z "${VIRTUAL_ENV}" ]; then
+    echo "Please make and activate a venv with your preferred tool, such as 'python -m venv ~/pom-venv; . ~/pom-venv/bin/activate' first."
+    exit 1;
+fi;
+
+pip install \
+    --upgrade \
+    --requirement ./requirements.txt \
+    --requirement ./dev-requirements.txt \
+    --requirement ./macOS-gui.requirements.txt \
+    --editable .