docs: Update documentation (#128)

Signed-off-by: jannfis <jann@mistrust.net>

1 files changed, 9 insertions, 0 deletions

diff --git a/docs/configuration/images.md b/docs/configuration/images.md
index 7643609..ee23a28 100644
--- a/docs/configuration/images.md
+++ b/docs/configuration/images.md
@@ -200,6 +200,15 @@ Valid values for `secret_ref` are:
   named `variable_name`. This can be a variable that is i.e. bound from a
   secret within your pod spec.
 
+* `ext:<path_to_script>` - Use credentials generated by a script. The script
+  to execute must be specified using an absolute path, and must have the
+  executable bit set. The script is supposed to output the credentials to be
+  used as a single line to stdout, in the format `<username>:<password>`.
+  Please note that the script will be executed every time Argo CD Image
+  Updater goes to find a new version, and credentials will not be cached. If
+  you want it to execute only once and cache credentials, you should configure
+  this secret on the registry level instead.
+
 In case of `secret` or `env`references, the data stored in the reference must
 be in format `<username>:<password>`