[Feature Request] In admin the variable has_change_permission in change_form.html should not be used for the breadcrumb menu

[Jannik Schürg]

In admin when rendering a change form the breadcrumb menu includes a link to the changelist, or only a text. The template’s variable has_change_permission is used to decide which to show.

As far as I understand the variable is set in ModelAdmin to has_change_permissions(request, obj) by default, but a user with has_change_permissions(request, obj=None) returning False will get a permission error clicking the link. I propose to take account of the possibility that the implication

has_change_permissions(request, obj) is True implies 

has_change_permissions(request, obj=None) is True

is not true.

The redirect behaviour in ModelAdmin's response_post_save_add et al. seems to handle this case. My implementation idea is to add another template variable in AdminModel's render_change_form.

If this change and implementation is welcomed I can try to create a patch if someone can provide guidance for what to do besides the two one line changes.

Greetings