The svn:externals property in the SVN can has date-time revisions instead of usual revision numbers:
svn complete replacement for externals : svn complete replacement for externals · Issue #243 · dirk-thomas/vcstool · GitHub
The format can contain dates:
-r “{2021-03-01 05:37:58 +0300}” “…@{2021-03-01 05:37:58 +0300}” …
-r “{2021-03-01T02:37:58.000000Z}” “…@{2021-03-01T02:37:58.000000Z}” …
So the resulted .gitsvnextmodules file would not has revision = XXX fields at all.
Svn tags contained just a branch directory copy plus change in svn:externals may left empty in the git, because a translated tag may has changes only in the revision = XXX fields and because it does not handle then, the git tag sourcetree diff would be empty.
The issue is first seen here:
``convert-svnexternals`` script does not handle ``svn:externals`` with date-time revisions : `convert-svnexternals` script does not handle `svn:externals` with date-time revisions · Issue #459 · newren/git-filter-repo · GitHub