How to perform efficient incremental update of a git repo from a large SVN repo? Bug or clueless user?

[James Mason <James.Mason@3ds.com>]

I have a large and active SVN repository.  More than 36,000 revisions,
thousands of branches - new ones created daily - and a non-standard
layout.  Also, a secondary git repository that serves as a faithful
"git" copy of the work accumulating in SVN (git version 2.9.5).  I seek
an efficient way to routinely (nightly?) update the git repo with new
changes accumulating in SVN.

Most of what I have found on the web suggests that, when properly
configured, incremental update will be correctly accomplished by "git
svn fetch".  My experience so far is that - while that will eventually
work - it is remarkably slow.  It's true that "git svn fetch" doesn't
redundantly add content - but it doesn't resume without appearing to
walk over all the old SVN revisions (watch the contents of
svn/.metadata).  For a large SVN repository - this can take days.

I initially posed this as a question on stack overflow (see "Routinely
updating a git repo from a large svn repo" ).  It appeared that I had
learned something about how to use "--revision" to speed things along -
so I recently added that as an answer to my own question (update now
taking routinely less than an hour).  Still that all seemed really odd.
"--revision" isn't documented as an option to "git svn fetch", you need
to dig START out of .git/svn/.metadata and END out of the SVN repository.

Today I searched on the string "branches-MaxRev" and found something
more explicitly at odds with my experience (in the git-svn document):

     Note that git-svn keeps track of the highest revision in which a
branch or tag has appeared. If the subset of
     branches or tags is changed after fetching, then
$GIT_DIR/svn/.metadata must be manually edited to remove
     (or reset) branches-maxRev and/or tags-maxRev as appropriate."

I read the documentation as saying that "git svn fetch" tracks where it
left off (which was my assumption before experiencing otherwise).   So
what I'm seeing seems like a bug - but I'm worried that my use of
"--revision" may not be entirely legitimate.

Any assistance, advice, etc., would be most appreciated.

-jrm

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