chore: update README for CLI

README.md

@@ -3,9 +3,21 @@
 ## Usage
 When building and customizing Frappe Doctypes (schema), tracking changes can be challenging. Relying on the current state of the UI doesn't show past changes, and git's diff does not reflect the functional change, only the line-by-line diff of the json file. This script and workflow displays a meaningful diff of the newest changes on pull requests and pushes in a runner terminal, and in the case of PRs, comments on the request.
 
-### Local Testing
-1. Change or delete any json files located in `/test_files`
-2. `bash ./run.sh`
+### CLI Usage
+Add the following to ~/.bashrc to use the mechanics of `git diff` while outputting the result of fsjd.
+
+```
+fdiff() {
+    (
+        export TABLE_MODE=1
+        export GIT_EXTERNAL_DIFF=~/fsjd/frappe_schema_json_diff.py
+        git --no-pager diff "$@"
+        unset GIT_EXTERNAL_DIFF
+    )
+}
+```
+
+For example, `fdiff HEAD HEAD~1` is equivalent to running `git --no-pager diff HEAD HEAD~1` with the GIT_EXTERNAL_DIFF environment variable set, and `git diff` will work normally afterward.
 
 ### CI Implementation
 Copy the file `.github/workflows/main.yaml` along with its parent directories into the root folder of a custom app. Change the branch on lines 4 and 6 if applicable. Keep the `1` on line 24 to print table diffs or change it to `0` for trees.
@@ -24,5 +36,10 @@ Runner terminals will show JSON file names and diff content for any modified fil
 | ------------------- | ------------------------------------- | ---------------------------------------------------------------------------------------------------------------- |
 | **json-source-map** | Fetching line numbers for diffed data | [PyPI](https://pypi.org/project/json-source-map/) [GitHub](https://github.com/open-alchemy/json-source-map/wiki) |
 | **Rich**            | Python output formatting              | [PyPI](https://pypi.org/project/rich/)             [GitHub](https://github.com/Textualize/rich)                  |
+
+### Local Testing
+1. Change or delete any json files located in `/test_files`
+2. `bash ./run.sh`
+
 ### Function
 A specific situation this tool is designed to account for is the deletion or reordering of elements in a list of dictionaries. If docfields (dictionaries) are added, deleted, or have their order changed, tools like DeepDiff will compare elements of the same index. FSJD will compare members of dictionary lists with matching common-key values. For example, docfields share the common-key 'field_name', so if two lists to be diffed contain dictionaries with this common-key, and their values match, those two dictionaries will be compared regardless of index. The tradeoff to this approach is that renaming a docfield (changing only the value of a common-key) will show a deleted and added docfield instead of a renamed value.