Q:

SVN: how to merge tags from separate projects

I have a single SVN repository with two separate projects:
project_1
    /trunk
    /branches
        /1.0
    /tags
        /1.0.0

project_2
    /trunk
    /branches
        /1.0
    /tags
        /1.0.0

As you can see, each has identical branch/tag numbers.  Imagine there are different files in each project.
I want to merge these into a single new project, project_3.  That is, the trunk of the new project will have all files/histories from the trunk of project_1 and project_2, the 1.0 branch will have all files/histories from the 1.0 branches of project_1 and project_2, and the 1.0.0 tag will have all files/histories from the 1.0.0 tags of project_1 and project_2.
My first thought was to do accomplish this using multiple svn cp executions. A big problem I ran into was not being able to copy just the subdirectories of a directory to another directory. I am having trouble understanding whether the solutions discussed in that post apply to the situation here.  Also, the post and many of the solutions are six years old and I wonder whether there have been any change to SVN that would help here.
The goal is to have a single unified project with as much history preserved as possible.  What is the best approach to take here?  Please note that switching to another VCS is not an option.

A:

If you want to merge data and history, you can't use SVN copy" you must to use dump|load cycles:
svnrdump sump URL/OF/DIR ... > dump + svnadmin load --ignore-uuid --parent-dir NEW_PARENT ... < dump
Instead of svnrdump you can try svnadmin dump | svndumpfilter

