llvm dev - Mar 2018 - local svn strategy for LLVM release updates

We are starting a local LLVM backend project (using svn) and are looking for a
mechanism to periodically update to later LLVM releases.
Certainly, this seems like it would be a relatively common use case and I
expected a google search would reveal several options.  However, I didn’t really
find anything.  Perhaps I’m not looking for the right keywords, if so please
help me out and point me to any relevant docs.
Could others share their experiences with maintaining local LLVM projects?

Without any further guidance, the path we will follow comprises of the following
flow:

Create a local repo with trunk/llvm_60
Copy trunk/llvm_60 to trunk/myproj60

Make project changes on trunk/myproj60

When LLVM 7.0 is released, create trunk/llvm_70 and copy this to trunk/myproj70

Diff trunk/llvm_60 with trunk/myproj60, identify and fix any conflicts, and
apply resulting patch to trunk/myproj70

Continue project development on trunk/myproj70


I’m pretty sure this will work, what I don’t like about it is that every 6
months we are rebasing our tree.  Assuming a successful project, over the years
we will have many rebased trees and finding a particular change/check-in will
require knowledge of which base a change was made.  I don’t know of any good
alternatives.

thanks
Doug


For completeness, I’ve included specific svn commands for starting with a LLVM
6.0 release and later upgrading to LLVM 7.0 below.

svnadmin create repos
svn mkdir file://`pwd`/repos/llvm
svn mkdir file://`pwd`/repos/llvm/trunk
svn mkdir file://`pwd`/repos/llvm/branches

svn export  http://llvm.org/svn/llvm-project/llvm/branches/release_60 llvm_60
svn import llvm_60 file://`pwd`/repos/llvm/trunk/llvm_60


svn copy trunk/llvm_60  file://`pwd`/repos/llvm/trunk/myproj60

//Make project changes to trunk/myproj60.

//When next llvm release is available (say llvm 7.0)


svn diff file://`pwd`/repos/llvm/trunk/llvm_60  
file://`pwd`/repos/llvm/trunk/myproj > /tmp/diffs60.patch
// Identify and fixup any conflicts, repeat above until no conflicts

// Repeat same steps as above to make a trunk/llvm_70 and trunk/myproj70
svn co file://`pwd`/repos/llvm/trunk/llvm_70 wc70

cd wc70
svn patch /tmp/diffs60.patch
svn commit

// Start using trunk/myproj70 as project base