Improve documentation for in-place builds

Author: pradyunsg

docs/html/reference/pip_install.rst

@@ -723,19 +723,25 @@ local hash.
 
 Local project installs
 ----------------------
+
 pip supports installing local project in both regular mode and editable mode.
 You can install local projects by specifying the project path to pip::
 
 $ pip install path/to/SomeProject
 
-Until version 20.0, pip copied the entire project directory to a temporary
-location and installed from there. This approach was the cause of several
-performance and correctness issues. As of version 20.1 pip installs from the
-local project directory. Depending on the build backend used by the project,
-this may generate secondary build artifacts in the project directory, such as
-the ``.egg-info`` and ``build`` directories in the case of the setuptools
-backend.
-
+pip generates a wheel distribution for the directory provided, that it uses
+to perform the installation. It may fall back to using ``setup.py install``
+if it is unable to generate a wheel distribution from the directory.
+
+Prior to pip 20.1, pip copied the entire project directory to a temporary
+location and attempted to generate the distribution from that directory.
+This approach was the cause of several performance issues, as well as various
+issues arising when the python project directory depends on its parent
+directory (such as the presence of a VCS directory). The main user visible
+effect of this change is that secondary build artifacts, if any, would be
+created in the local directory, whereas earlier they were created in a
+temporary copy of the directory and then deleted. This notably includes the
+``build`` and ``.egg-info`` directories in the case of the setuptools backend.
 
 .. _`editable-installs`:
 

news/7555.removal

@@ -1,9 +1,2 @@
-Building of local directories is now done in place. Previously pip did copy the
-local directory tree to a temporary location before building. That approach had
-a number of drawbacks, among which performance issues, as well as various
-issues arising when the python project directory depends on its parent
-directory (such as the presence of a VCS directory). The user visible effect of
-this change is that secondary build artifacts, if any, may therefore be created
-in the local directory, whereas before they were created in a temporary copy of
-the directory and then deleted. This notably includes the ``build`` and
-``.egg-info`` directories in the case of the setuptools build backend.
+Building of local directories is now done in place, instead of a temporary
+location containing a copy of the directory tree.