What would you like to be added?

Add an ability to set Delims (https://pkg.go.dev/text/template#Template.Delims) in go templates.

I think it could be done using cli-flags or something like that.

All we need is add Delims function after all New functions (like here:

It could be something like that but without hardcoded values

t.New(filename).Delims("[%", "%]").Parse(r.tpl)

Why is this needed?

When we have several layers of templating (something like jinja2+helm) it is required to use some ugly approaches to escape helm templating while files are templating by another engine first.

I know that jinja2 can change its own delimiters but it is just an example - it could be another engine which also uses {{ and }} but without ability to change them.

Another example with PrometheusRule.

We have to do something like that:

        - alert: GitlabRunnerMissingExportMount
          expr: gitlab_runner_missing_export
          for: 5m
          labels:
            gitlabrunner: count
          annotations:
            summary: |-
              GitLab Runner missing /export mountpoint
            description: |-
              GitLab Runner '{{ printf "{{ $labels.gitlab_runner_name }}" }}' does not have '/export' filesystem mounted.

With custom delimiters it could be just:

        - alert: GitlabRunnerMissingExportMount
          expr: gitlab_runner_missing_export
          for: 5m
          labels:
            gitlabrunner: count
          annotations:
            summary: |-
              GitLab Runner missing /export mountpoint
            description: |-
              GitLab Runner '{{ $labels.gitlab_runner_name }}' does not have '/export' filesystem mounted.

And the whole value would be passed to manifest to allow prometheus use it as is.