Update functorch README to reflect move into PyTorch (#85832)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/85832
Approved by: https://github.com/Chillee

functorch/README.md

@@ -39,7 +39,7 @@ transforms comes from the [JAX framework](https://github.com/google/jax).
 
 There are two ways to install functorch:
 1. functorch from source
-2. functorch beta (compatible with PyTorch 1.11)
+2. functorch beta (compatible with recent PyTorch releases)
 
 We recommend trying out the functorch beta first.
 
@@ -54,37 +54,11 @@ Follow the instructions [in this Colab notebook](https://colab.research.google.c
 
 #### Locally
 
-First, set up an environment. We will be installing a nightly PyTorch binary
+As of 9/21/2022, `functorch` comes installed alongside a nightly PyTorch binary.
-as well as functorch. If you're using conda, create a conda environment:
+Please install a Preview (nightly) PyTorch binary; see  https://pytorch.org/
-```bash
+for instructions.
-conda create --name functorch
-conda activate functorch
-```
-If you wish to use `venv` instead:
-```bash
-python -m venv functorch-env
-source functorch-env/bin/activate
-```
 
-Next, install one of the following following PyTorch nightly binaries.
+Once you've done that, run a quick sanity check in Python:
-```bash
-# For CUDA 10.2
-pip install --pre torch -f https://download.pytorch.org/whl/nightly/cu102/torch_nightly.html --upgrade
-# For CUDA 11.3
-pip install --pre torch -f https://download.pytorch.org/whl/nightly/cu113/torch_nightly.html --upgrade
-# For CPU-only build
-pip install --pre torch -f https://download.pytorch.org/whl/nightly/cpu/torch_nightly.html --upgrade
-```
-If you already have a nightly of PyTorch installed and wanted to upgrade it
-(recommended!), append `--upgrade` to one of those commands.
-
-Install functorch:
-```bash
-pip install ninja  # Makes the build go faster
-pip install --user "git+https://github.com/pytorch/functorch.git"
-```
-
-Run a quick sanity check in python:
 ```py
 import torch
 from functorch import vmap
@@ -95,28 +69,20 @@ assert torch.allclose(y, x.sin())
 
 #### functorch development setup
 
-`functorch` is a PyTorch C++ Extension module. To install,
+As of 9/21/2022, `functorch` comes installed alongside PyTorch and is in the
+PyTorch source tree. Please install
+[PyTorch from source](https://github.com/pytorch/pytorch#from-source), then,
+you will be able to `import functorch`.
 
-- Install [PyTorch from source](https://github.com/pytorch/pytorch#from-source).
+Try to run some tests to make sure all is OK:
-`functorch` usually runs on the latest development version of PyTorch.
-- Run `python setup.py install`. You can use `DEBUG=1` to compile in debug mode.
-
-Then, try to run some tests to make sure all is OK:
 ```bash
 pytest test/test_vmap.py -v
 pytest test/test_eager_transforms.py -v
 ```
 
-To do devel install:
+AOTAutograd has some additional optional requirements. You can install them via:
-
 ```bash
-pip install -e .
+pip install networkx
-```
-
-To install with optional dependencies, e.g. for AOTAutograd:
-
-```bash
-pip install -e .[aot]
 ```
 
 To run functorch tests, please install our test dependencies (`expecttest`, `pyyaml`).
@@ -125,7 +91,7 @@ To run functorch tests, please install our test dependencies (`expecttest`, `pyy
 </p>
 </details>
 
-### Installing functorch beta (compatible with PyTorch 1.11)
+### Installing functorch beta (compatible with recent PyTorch releases)
 
 <details><summary>Click to expand</summary>
 <p>
@@ -136,7 +102,7 @@ Follow the instructions [here](https://colab.research.google.com/drive/1GNfb01W_
 
 #### pip
 
-Prerequisite: [Install PyTorch 1.11](https://pytorch.org/get-started/locally/)
+Prerequisite: [Install PyTorch](https://pytorch.org/get-started/locally/)
 
 
 ```bash