doc: Added instructions to create a patch file

Signed-off-by: Brandon Groth <[email protected]>

Author: BrandonGroth

patches/README.md

@@ -8,4 +8,21 @@ python3 install_patches.py
 ```
 
 The following optional packages require a patch:
-* `microxcaling`: Uses outdated versions of PyTorch-related packages
+* `microxcaling`: Uses outdated versions of PyTorch-related packages
+
+## Making a Patch File
+To make a git diff patch file, first make your desired changes to the repository.  Then run
+```
+git diff > <package>.patch
+```
+Packages may include files that differ by whitespaces even if you didn't change them.
+To address this, add `--ignore-all-spaces` to the `git diff` command.
+
+To test the patch file, copy the `<package>.patch` file to `fms-model-optimizer/patches`.
+Next add a new entry to the `install_patches.py` dictionary called `dependencies_with_patch` with the package name and repo URL:
+```
+dependencies_with_patch = {
+    <package>: <URL>, # for <package>.patch
+}
+```
+Lastly, run the python command for `install_patches.py`.