Add documentation note re: git-pre-pull vs. auth

docs/development/plugin-triggers.md

@@ -321,6 +321,10 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 # TODO
 ```
 
+> WARNING: The `git-pre-pull` trigger should _not_ be used for authentication
+since it does not get called for commands that use `git-upload-archive` such
+as `git archive`. Instead, use the [`user-auth`](#user-auth) trigger.
+
 ### `install`
 
 - Description: Used to setup any files/configuration for a plugin.