docs: getting-started: Improve "running pip from source tree" section

Also add news entry

docs/html/development/getting-started.rst

@@ -34,12 +34,16 @@ For developing pip, you need to install :pypi:`tox`. Often, you can run
 Running pip From Source Tree
 ============================
 
-To run the pip executable from your source tree during development, run pip
-from the ``src`` directory:
+To run the pip executable from your source tree during development, install pip
+locally using editable installation (inside a virtualenv).
+You can then invoke your local source tree pip normally.
 
 .. code-block:: console
 
-    $ python src/pip --version
+    $ virtualenv venv # You can also use "python -m venv venv" from python3.3+
+    $ source venv/bin/activate
+    $ python -m pip install -e .
+    $ python -m pip --version
 
 
 Running Tests

news/8148.trivial

+Improve "Running pip from source tree" section in getting-started
+to use editable installation instead of running pip directly from source.