Update to reflect changes from helm/helm#10299

* use modifier `delimiters=` instead of `delim=`
* specify full delimiters instead of duplicating the delimiter (`[,]` -> `[[,]]`)
* document the Template Header concept

Signed-off-by: Neer Friedman <neerfri@gmail.com>

hips/hip-9999.md

@@ -10,7 +10,7 @@ status: "draft"
 ## Abstract
 
 Many tools use templating syntax with `{{ ... }}` delimiters, it's hard to maintain Helm charts for such tools.
-This HIP suggests to use "magic comments" in the template to control the delimiter.
+This HIP suggests to use "magic comments" (AKA modelines) in the template to control the delimiter.
 
 ## Motivation
 
@@ -26,10 +26,10 @@ a chart maintainer to only use the feature for templates that really need it and
 
 ## Specification
 
-To change the template delimiter, a helm user would add a `# helm: delim=[,]` comment to the head of the template file:
+To change the template delimiter, a helm user would add a `# helm: delimiters=[[,]]` comment to the head of the template file:
 
 ```yaml
-# helm: delim=[,]
+# helm: delimiters=[[,]]
 apiVersion: v1
 kind: ConfigMap
 metadata:
@@ -38,13 +38,13 @@ data:
   myvalue: "Hello {{world}}"
 ```
 
-It's worth mentioning that the delimiter set in the `# helm: delim=[,]` is doubled in the actual template.
-This is because otherwise the comment `# helm: delim=[[,]]` would make the template engine try to execute `[[,]]` and fail.
+Magic comments will be read from the **Template Header**, all initial lines in a template upto the first line that does not start with "#".
+The **Template Header** will be rendered in the final output but will not be processed by the template engine.
 
 
 ## Backwards compatibility
 
-The feature will have no effect on charts that do not contain the `# helm: delim=[,]` comment.
+The feature will have no effect on charts that do not contain the `# helm: delimiters=[[,]]` comment.
 As such it has no backwards compatibility issues.
 
 Given that the most likely reason to use the feature is the use of `{{ ... }}` in a chart template,