Add Template name function to help trace/debug templates

[mdhender]

Add a function that writes the name of the template. This would help when tracing the output of templates.

An example would be:

func TemplateName(a string) template.HTML {
  return template.HTML("<!-- hugo: " + a + " " + template.Name() + " -->\n");
}

Called like:

{{ TemplateName "enter" }}
. . . do something . . .
{{ TemplateName "leave" }}

With results like:

<!-- hugo: enter _thisTemplatesName_ -->
. . . something . . .
<!-- hugo: leave _thisTemplatesName_ -->

[digitalcraftsman]

There is a related forum thread

[bep]

This issue has been automatically marked as stale because it has not been commented on for at least four months.

The resources of the Hugo team are limited, and so we are asking for your help.

If this is a bug and you can still reproduce this error on the master branch, please reply with all of the information you have about it in order to keep the issue open.

If this is a feature request, and you feel that it is still valuable, please open a proposal at https://discuss.gohugo.io/.

This issue will automatically be closed in four months if no further activity occurs. Thank you for all your contributions.

[bep]

Note/Update: This issue is marked as stale, and I may have said something earlier about "opening a thread on the discussion forum". Please don't.

If this is a bug and you can still reproduce this error on the latest release or the master branch, please reply with all of the information you have about it in order to keep the issue open.

If this is a feature request, and you feel that it is still relevant and valuable, please tell us why.

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.