Clarify search parameter in the branches API docs

doc/api/branches.md

@@ -19,10 +19,9 @@ GET /projects/:id/repository/branches
 Parameters:
 
 | Attribute | Type           | Required | Description |
-|:----------|:---------------|:---------|:-------------------------------------------------------------------------------------------------------------|
-| `id`      | integer/string | yes      | ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user. |
-| `search`  | string         | no       | Return list of branches matching the search criteria.                                                        |
-
+|:----------|:---------------|:---------|:------------|
+| `id`      | integer/string | yes      | ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user.|
+| `search`  | string         | no       | Return list of branches containing the search string. You can use `^term` and `term$` to find branches that begin and end with `term` respectively.|
 Example request:
 
 ```sh