Here is my scenario:
a upstream Git tag 1.2 has been used as first commit in an empty Subversion repository without git svn. Files have been copied and added into Subversion trunk working copy.
in Subversion, a small list of changesets have been committed in /trunk
I now would like to use a Git fork from original upstream (large repository) and import these Subversion changesets into a feature branch created from initial tag 1.2.
There is no branch or tag in Subversion repository I am interested in importing into upstream Git repository.
My first trial with git-svn was not successful because the branch created as no common ancestor with upstream history. How should I import my Subversion changesets to be able to operate merge in Git then ?
I think your take with using git svn is ok here.
You can either force the merge of unrelated histories with using --allow-unrelated-histories as parameter to the merge command.
Or you can just use git cherry-pick to reapply your newly imported commits on top of the Git tag.