On Fri, Feb 1, 2013 at 1:49 AM, Ivan Zhakov <i...@visualsvn.com> wrote: > On Wed, Jan 23, 2013 at 9:39 PM, Paul Burba <ptbu...@gmail.com> wrote: >> On Wed, Jan 23, 2013 at 9:51 AM, Julian Foad <julianf...@btopenworld.com> >> wrote: >>> Ivan Zhakov wrote: >>> >>>> I was testing recent changes in ra_serf update editor and noticed that >>>> reintegrate-like merges for long living branches are extremely slow. >>>> Client requests server for diff between branches with respect to >>>> ancestry and servers reports no-op txdelta for every file that was >>>> changed in original branch. Then for every such file client retrieves >>>> text and properties. >>>> >>>> For example try to reintegrate ev2-export branch back to trunk. > [...] > > Hi Bert and Paul! > > On Wed, Jan 23, 2013 at 6:51 PM, Bert Huijben <b...@qqmail.nl> wrote: >> Is there a way the diff code can see that it receives a no-op txdelta? >> >> In that case it can just skip retrieving the file as it won't be able to >> produce a difference anyway. >> > It would be really hard to implement on client, because no-op txdelta > transmitted as full txdelta with instructions to copy all source data. > > But we can detect such no-op txdelta on server side. See my plan bellow. > >>> Thanks Ivan, that's very interesting. I'll take a look, since I have just >>> been working on that code. >>> >>> I exposed this as a separate option because the >> two meanings of the previous 'ignore_ancestry' option were conflated, but I >> don't deeply understand what happens when this option is specified. I know >> what it's >> supposed to mean at a basic level: "diff a pair of unrelated nodes as if >> they are related". What I don't know is how well it's implemented and >> whether it's really useful when merging. >>> >>>> What is the purpose of diff_ignore_ancestry for merges? Can we default >>>> it to FALSE? >>> >>> I assume one of the purposes is if your work flow has been such >> that a file is sometimes replaced (without copy-from) >> >> Any replacement is a problem, regardless of copy-from. For example: >> > > [...] > >> >>>, and sometimes a new file added on one branch has been added on the >> other branch by a simple add (without copy-from). In that sort of work flow, >> the 'diff_ignore_ancestry' would cause Subversion to do diffs between >> different versions of a file, and that might well help in merging the >> changes. >> Without the 'diff_ignore_ancestry' option, Subversion would treat the file as >> 'replaced', and so you'd be likely to get a tree conflict when you try to >> merge it. >> > Thanks for demonstrating use-case. That what I was looking for. We > cannot change to ignore_ancestry = TRUE by default, but I'm going to > try the following: > 1. Add test case for replacement merge that you demonstrated (it would > be useful anyway) > Test added in r1441400.
> 2. Modify delta reporter on server side to do not send deltas if files > have the same content, regardless ancestry (see > subversion/libsvn_repos/reporter.c:696 delta_files()) Patch attached. > The new test for merge replacements also passes with my patch. So I'm going to cleanup it and commit after further testing. > 3. Test it and think a little bit more is it safe change or not :) > -- Ivan Zhakov
