Clarify lack of support for a couple of features available with the b…

…uilt-in Git material

README.md

@@ -16,7 +16,7 @@ This is the missing GoCD support for [mono-repos](https://developer.atlassian.co
 * Provide **clean, filtered change logs** for pipeline/VSM comparisons showing only changes on the monitored paths within a repository
 
 This plugin is intended as 
-* a **drop-in replacement** for the built-in GoCD Git material
+* a **drop-in replacement** for the built-in GoCD Git material (see [known issues](#known-issues) for some caveats)
 * replaces the problematic use of **whitelists** and **blacklists**
   * whitelists and blacklists in GoCD tend to prevent/block fan-in because materials with different whitelists are still considered equivalent
   by the fan-in algorithm. This makes them unsuitable for use as environment side-channels or dealing with mono-repos.
@@ -103,21 +103,40 @@ configure your pipelines as code; you can update the id per the above example.
 
 ### Known issues
 
-*Creating new pipelines via UI on pre `19.8.0` GoCD versions*
+#### No support for GoCD server secrets management
 
-You will *not* be able to see *Git Path* material as a material type when creating a new pipeline. 
-Add a dummy git material, then edit to add a new *Git Path* material and remove the old one. This problem
-has been resolved in newer GoCD versions via the pipeline creation wizard.
+Custom source control material plugins like the `gocd-git-path-material-plugin` do not have password variables interpolated 
+and populated by the GoCD server using its support for [secrets management](https://docs.gocd.org/current/configuration/secrets_management.html). 
+You can see https://github.com/TWChennai/gocd-git-path-material-plugin/issues/28 and https://github.com/gocd/gocd/issues/8234 for
+more detail.
+
+If you use pipelines-as-code to source control your material definitions, it is instead possible to use SSH keys within 
+your GoCD server and agent to authenticate with a private repository. If running GoCD on Kubernetes, there is support for 
+doing so based on Kubernetes `Secret`s within the [GoCD Helm chart](https://github.com/helm/charts/tree/master/stable/gocd)
+or any other solution that allows mounting of a file into a container.
+
+#### No support for triggering from webhooks
+
+Custom source control material plugins like the `gocd-git-path-material-plugin` do not have support for 
+[triggering from webhooks](https://api.gocd.org/current/#webhook), as opposed to the convention material polling approach.
+You can see https://github.com/TWChennai/gocd-git-path-material-plugin/issues/27 and https://github.com/gocd/gocd/issues/8170 for
+more detail.
 
-*Stale data in agent repository clones*
+#### Stale data in agent repository clones
 
 This plugin uses Git commands to filter the history and determine the most recent revision that matches the
 monitored paths. This means that changes that are not monitored in your paths may be "stale". The plugin does
-not `rm` un-monitored paths from a clone; meaning your build task could accidentally be depending on files in the
+not `rm` un-monitored paths from a clone; meaning your build task could accidentally depend on files in the
 repository that are out-of-date.
 
 Be careful with your repository structure to keep your monitored path expressions simple.
 
+#### Creating new pipelines via UI on pre `19.8.0` GoCD versions
+
+You will *not* be able to see *Git Path* material as a material type when creating a new pipeline. 
+Add a dummy git material, then edit to add a new *Git Path* material and remove the old one. This problem
+has been resolved in newer GoCD versions via the pipeline creation wizard.
+
 ### Contributing
 
 #### Build