Merges from release branches to vendor tracking branches

[Joseph Myers]

On Thu, 23 Jan 2020, Jakub Jelinek wrote:

> Just FYI if somebody needs to do something similar, I needed to do a merge
> from origin/releases/gcc-9 to our vendor branch - 
> refs/vendors/redhat/heads/gcc-9-branch
> This branch has some extra commits origin/releases/gcc-9 branch doesn't
> have, so it is not a fast forward merge and we have the requirement that
> From-SVN: shouldn't appear in commit logs of new commits.

That's only meant to apply to new commits, not those merged in.  The call 
to check_revision_history (where we inserted the checks for From-SVN) is 
conditional on "not commit.pre_existing_p".

-- 
Joseph S. Myers
joseph@codesourcery.com