Re: Subversion Mirror

On Thu, Oct 21, 2021 at 5:19 PM Warner Losh <imp@bsdimp.com> wrote:

> Greetings,
>
> This email documents two recent events with the git -> subversion mirror.
> This seems like the best way to document these two issues given their
> esoteric nature.
>
> We stopped mirroring stable/12 about a week ago. The root cause of this
> outage was traced to there being an empty commit that was merged. This
> caused the git cherry-pick that we do to bring these into the git-svn tree
> that we use to publish to subversion to fail. The code has been updated to
> handle these commits in the future. In the future, empty commits will
> simply be skipped. Kyle did these commits to record a commit/backout pair
> had been 'merged' so that they stopped showing up in the tools as merge
> candidates. Since this metadata exists only in the git world, dropping them
> in the subversion world is fine (we've stopped updating mergeinfo data for
> stable/12).
>
> The second incident was when the BETA1 builds were delayed by 23 hours.
> This was due to the creation of the releng/12.3 branch in git. This is our
> first new releng branch since we started mirroring to svn and the process
> was not documented by the author of the git to subversion script (namely
> me). It took me a while to understand why simply creating the branch was
> insufficient and to realize the proper path forward.
>
> The proper sequence of events is to create new releng/12.x branch from the
> branch point by hand in subversion. All these things should be done as user
> git2svn:
>
> % svn copy file:///home/svn/base/stable/12@r370949
> file:///home/svn/base/releng/12.3 -m 'Create releng/12.3'
>
> where r370949 was the point in subversion where releng/12.3 was branched.
>

There turned out to be a problem with this. In git when you create a
branch, you make changes to it, unlike in subversion. So when I did the
above copy, it got the branch point correct, but lost the changes that went
along with the branch creation. I had to
cherry-pick 27c4d9242bf086f2038defcd458bb4b146892add (the first change on
the releng/12.3 branch) to make things the same and landed the change. Had
I to do it again, I'd have written a script to do the git svn dcommit and
the git propset to set the commit's name to gjb. I did the latter too
slowly and the repo as mirrored with git2svn as the author name, so I
changed it back. subversion is terrible about fixing bad metadata once it
gets mirrored, so this is the lessor of the various evils.

Warner


> Once this branch was created, the 'git-svn' pump needed to be primed. The
> releng123 branch needed to be added to ~git2svn/git2svn.conf file (and but
> not to the list of branches= yet):
>
> # releng/12.3 config
> releng123_name="releng/12.3"
> releng123_path=/home/git/freebsd-src-releng-12.3
>
> Once that was done, we needed to initialize the git2svn tree that lives on
> git2svn.freebsd.org, as the user git2svn:
>
> % ./gsm2 -b releng123 branch-init
>
> which will create the necessary git-svn tree for the crontab's 'gsm2
> mirror' command to work. Once the branch has been initialized, releng123
> should be added to the branches= so that commits start to flow.
>
> These issues have been corrected, so the git -> svn mirror hopefully will
> go back to being a background process that just works. One could argue this
> should be automated. I've chosen not to automated it because it's a lot
> more effort to do that than to document the process should we have a
> 12.4-RELEASE in the future (and its associated releng/12.4).
>
> Finally, we're still mirroring the 11.x branches. This will stop at some
> point in the future, though, most likely the next time the mirroring of
> 11.x breaks :).
>
> Warner
>