The 1992-2007 era of PLplot development used CVS as the revision
control system.  The pre-existing CVS repo was installed at
SourceForge when PLplot was first registered as a project there in
2000.  Subsequently it was discovered there were some issues with some
of the files that had been historically deleted (stored internally in
the CVS "Attic") such that those files became resurrected from the
dead again by any attempt to export from CVS or establish a CVS
branch.  Identifying the names of those files and CVS deleting them
(presumably for the second time, but this time it "took") solved that
issue, but left us with a feeling that the CVS software that had
historically been used with our repo from 1992 to 2000 was probably
not too reliable, and potentially could have left other issues in our
CVS repo.

Despite such potential issues with our CVS repo, we decided to attempt
to preserve all our history by converting that CVS repo to subversion
in 2007 rather than simply starting all over with subversion with a
copy of our latest source tree.  The externally supplied script used
to do the conversion was called cvs2svn.  And because of concerns
about problems with the CVS repo data, results were carefully checked
by comparing CVS and svn logs in detail, and also doing detailed tree
diffs of the CVS versus svn results for branches, tags, and trunk.
Such checks caught a few issues such as binary files being clobbered
in the transformation to svn because they were improperly identified
as text files for CVS, but ultimately all those issues were sorted out
and the result was a good subversion repository for PLplot that
contained all the PLplot development history (commit messages and
files) back to 1992.

PLplot development continued from 2007 to 2014 with subversion with no
repository issues ever showing up.  But in 2014 we decided to use
the git distributed revision control system instead of subversion.
For details about that conversion process (which also preserved all
our history back to 1992) see README_svn2git_conversion