Add info about the repo override file

readme.md

@@ -16,7 +16,7 @@ Looks for the `managed-files` custom property on a repo, and parses out a comma
 
 For example, the value could be: `group:base,go-test`. This would pull in the base group of files and the go-test file.
 
-### Config Format
+## Config Format
 
 ```yaml
 groups:
@@ -54,3 +54,13 @@ files:
 * `template_name` is the name of the template to use from the supplied templates directory
 * `repo_path` is the path within the repo to place the file
 * `alternate_paths` is a list of alternate/equivalent paths this template might have been named before being managed. These files will be renamed and updated to the latest version of the template, if present
+
+## Repo Overrides
+
+If you need to override any of the default settings on a per-repo basis, you can create a [.repo-content-updater.yaml](examples/.repo-content-updater.yaml) file in the root of the repo, and configure any overrides there. It must be present in the default branch of the repo to be loaded.
+
+* `pr_target_branch` is the branch to target PRs against. This is the default branch by default, but if this is overridden in the repo, the branch will be created from and targeted against the supplied branch
+* `assign_users` is a list of GitHub users to assign the PR to instead of the default review team. If set, the default review team will not be used. This can be used (if desired) in combination with the `assign_group` field of the repo config file
+* `assign_group` is a group to assign the created PRs to. This can be used (if desired) in combination with the `assign_users` field of the repo config file
+* `commit_prefix` will set a common prefix on any commits generated by this tool.
+* `var_overrides` will override the default values for templates with values supplied here