feat: Adding documentation about the customizations done in the repo by Shorebird

README.md

@@ -26,6 +26,7 @@ open source.
 * [Flutter documentation](https://docs.flutter.dev/)
 * [Development wiki](https://github.com/flutter/flutter/wiki)
 * [Contributing to Flutter](https://github.com/flutter/flutter/blob/master/CONTRIBUTING.md)
+* [Shorebird's customizations](./shorebird.md)
 
 For announcements about new releases, follow the
 [flutter-announce@googlegroups.com](https://groups.google.com/forum/#!forum/flutter-announce)

shorebird.md

@@ -0,0 +1,48 @@
+# Shorebird's change in the Flutter Repo 🐦
+
+This repository is the fork of the [Flutter](https://github.com/flutter/flutter) repository
+with the changes necessary to support [Shorebird](https://shorebird.dev).
+
+This document lists and explains these changes.
+
+## Flutter Tools
+
+The [Flutter Tools](./packages/flutter_tools) contains code that might alter the `shorebird.yaml`
+file originally created by the user.
+
+Changes on the file are done only on bundled files, and the user's file is not altered.
+
+The changes are:
+
+> `app_id` when using Flavors
+
+When using Flavors, a `shorebird.yaml` might look like this:
+
+```yaml
+app_id: 1
+flavors:
+  global: 2
+  internal: 3
+```
+
+When the user executes a shorebird release/patch command, using a flavor, the file will be updated
+to set the app id to the flavor's app id, so if using the `internal` flavor, the file will look like this:
+
+```yaml
+app_id: 3
+```
+
+You can find these customizations in the following source files:
+ - [Android](https://github.com/shorebirdtech/flutter/blob/shorebird/dev/packages/flutter_tools/gradle/src/main/groovy/flutter.groovy#L1337)
+ - [iOS](https://github.com/shorebirdtech/flutter/blob/shorebird/dev/packages/flutter_tools/lib/src/ios/mac.dart#L563)
+
+> Adds `patch_public_key` when a key encoded key is provied
+
+When an encoded public key is provided via the `SHOREBIRD_PUBLIC_KEY` environment variable. The
+`shorebird.yaml` file will be updated to include the `patch_public_key` attribute containing the
+value received.
+
+This is done just on Android at this moment.
+
+You can find these customizations in the following source files:
+ - [Android](https://github.com/shorebirdtech/flutter/blob/shorebird/dev/packages/flutter_tools/gradle/src/main/groovy/flutter.groovy#L1339)