Subversion support for "View annotation prior to this change"
The "View annotation prior to this change" feature added in #35432 currently only supports Git. This issue is for implementing the feature for Subversion as well.
Robert Korulczyk wrote in #35432#note-9:
However, `blame` / `annotate` subcommand of other SCMs such as subversion doesn't give the information of the previous change, so we have to find another way to get the previous change.
You don't really need to know revision of previous change for SVN. Since revisions in SVN are sequential numbers, you only need to decrease number of revision of given change and show annotations for this version. For example to see annotations prior r22231 for this file
you need to show annotations for revision 22230: https://www.redmine.org/projects/redmine/repository/svn/revisions/22230/annotate/trunk/app/views/repositories/revision.html.erb