On Mon, 2009-12-14, Paul Burba wrote: > On Wed, Oct 14, 2009 at 8:23 PM, Julian Foad <[email protected]> > wrote: > > * STATUS: Update my review status on r39019. [...] > > ^/branches/1.6.x-r39109
(The branch is now correctly named "...-r39019" so I've corrected that reference to it.) > > Votes: > > +1: pburba > > - -0: julianfoad (tried to review but got stuck trying to understand > > what > > - combine_with_lastrange() is meant to do, > > + -0: julianfoad (reviewed the changes in mergeinfo.c only; > > and also it seems to sneak in another bug fix in > > fix_deleted_subtree_ranges(). I suggest splitting up this patch.) > > Hi Julian, > > Here is why that change is included: [...] Hi Paul. Thank you for the explanation. I've had another look and given it a +1. - Julian > svn_rangelist_* APIs have always required forward rangelists: > > * (b) A "rangelist". An array (@c apr_array_header_t *) of non-overlapping > * merge ranges (@c svn_merge_range_t *), sorted as said by > * @c svn_sort_compare_ranges(). An empty range list is represented by > * an empty array. Unless specifically noted otherwise, all APIs require > * rangelists that describe only forward ranges, i.e. the range's start > * revision is less than its end revision. > > Prior to r879093(r40041) > libsvn_client/merge.c:fix_deleted_subtree_ranges() called > svn_rangelist_diff() with reversed ranges. We simply lucked out that > this has never caused any *known* problems. AFAICT this abuse of the > svn_rangelist_diff API in fix_deleted_subtree_ranges() could never > cause an incorrect merge/error/assert in practice(1) prior to > r879093... > > ...But r879093 added the helper function > libsvn_subr/mergeinfo.c:get_type_of_intersection() which is ultimately > used by all the svn_rangelist_* and svn_mergeinfo_* APIs and is > written assuming only forward merges are passed in; the function > asserts if reverse ranges are passed to it. So if I were to create a > backport branch of r879093 minus the change to > fix_deleted_subtree_ranges(), this assert would get triggered in > previously working merges. In our test suite this can be seen in > merge_tests.py 65 'child having different rev ranges to merge'. I'm > pretty certain nobody would approve a backport which breaks the test > suite. > > I endeavor to keep each commit a logically discrete change, but in > this case I think the fix of fix_deleted_subtree_ranges()'s API abuse > is so interdependent with the core fix of r879093 that it made little > sense to commit them separately. Even if I had, they would both be > nominated as a group for backport. > > Paul > > (1) I hesitate to get into to much detail why this is (it hardly seems > relevant), but briefly this seems never to have bitten us due to the > call to filter_merged_revisions() immediately preceding > svn_rangelist_diff() in > fix_deleted_subtree_ranges(calculate_remaining_ranges on the 1.6.x > branch). This removes any requested reverse merges which are not > represented in explicit/implicit mergeinfo. In combination with the > temporary inheritable mergeinfo created by a merge under any paths > with non-inheritable mergeinfo in the merge target, I can't find any > combination or merges that would create a situation where a reverse > merge would break, though this is quite dependent on the current > implementation of get_type_of_intersection(). Assuming there were no > asserts, an equally valid implementation of get_type_of_intersection > could easily produce incorrect merges.
