Update development notes

Author: virtuald

README.md

@@ -37,6 +37,27 @@ Then run this command to build all the wheels.
 
 All the resulting wheels are in `dist`, which can be installed using `pip`.
 
+
+Development environment
+-----------------------
+
+To install all robotpy packages in [editable mode](https://packaging.python.org/en/latest/guides/distributing-packages-using-setuptools/#working-in-development-mode)
+run this:
+
+    ./rdev.sh develop
+
+For pure python development, you can just edit the files in this repository in-place, and
+changes will take effect immediately.
+
+If you are changing C++/wrapper code, you will need to rebuild the package that you are
+modifying. You can either run the develop command above (which rebuilds everything) or
+rebuild an individual package:
+
+    ./rdev.sh develop NAME
+
+It can be a slow process,see the [robotpy-build documentation](https://robotpy-build.readthedocs.io/en/stable/tips.html)
+for tips to make it more efficient.
+
 Cross Compilation
 -----------------
 

devtools/__main__.py

@@ -39,11 +39,20 @@ def info(ctx: Context):
 
 
 @main.command()
+@click.argument("package", required=False)
 @click.pass_obj
-def develop(ctx: Context):
-    """Install all robotpy packages in editable mode"""
-    for project in ctx.subprojects.values():
-        project.develop()
+def develop(ctx: Context, package: str):
+    """Install robotpy packages in editable mode"""
+    if package:
+        for project in ctx.subprojects.values():
+            if project.name == package:
+                project.develop()
+                break
+        else:
+            raise click.BadParameter(f"invalid package {package}")
+    else:
+        for project in ctx.subprojects.values():
+            project.develop()
 
 
 @main.command()