Add values templating information

docs/gitrepo-content.md

@@ -89,6 +89,11 @@ __How changes are applied to `values.yaml`__:
 
 - When changes are applied to the `values.yaml` from multiple sources at the same time, the values will update in the following order: `helm.values` -> `helm.valuesFiles` -> `helm.valuesFrom`. That means `valuesFrom` will take precedence over both, `valuesFiles` and `values`.
 
+![](/img/FleetValuesStages.svg)
+
+The targeting step can treat the values as a template and fill in information from the `clusters.fleet.cattle.io` resource. More information can be found in [Helm values templating](./ref-fleet-yaml#templating).
+This can be turned off in `fleet.yaml`, by setting `disablePreProcess`, e.g. to avoid conflicts with other templating languages.
+
 :::note Credentials in Values
 
 If the chart generates certificates or passwords in its templates, these values must be overriden. Otherwise the chart could be continuously deployed as these values change.

docs/ref-fleet-yaml.md

@@ -395,10 +395,14 @@ Values are processed in different stages of the lifecycle: https://fleet.rancher
 It is possible to specify the keys and values as go template strings for
 advanced templating needs.  Most of the functions from the [sprig templating
 library](https://masterminds.github.io/sprig/) are available.
+This can be turned off in `fleet.yaml`, by setting `disablePreProcess`, e.g. to
+avoid conflicts with other templating languages.
 
 Note that if the functions output changes with every call, e.g. `uuidv4`, the
 bundle will get redeployed.
 
+You can [test values templating with the CLI](./ref-bundle-stages#fleet-target) against existing clusters.
+
 The template context has the following keys:
 
 * `.ClusterValues` are retrieved from target cluster's `spec.templateValues`
@@ -426,3 +430,13 @@ will result in the following text:
 ```
 foo-bar-${PWD}
 ```
+
+:::warning empty values
+It is easier to use `global.fleet.clusterLabels.LABELNAME` instead of templating. When using templating, make sure to protect against null values.
+
+Example:
+```
+${ if hasKey .ClusterLabels "LABELNAME" }${ .ClusterLabels.LABELNAME }${ else }missing${ end}
+```
+:::
+