exchange: backout changeset c26335fa4225 Changeset c26335fa4225 has good intends but introduce significant behavior regressions for multiple important cases. In short there are many case where push would have caught instability creation/propagation that are no longer covered. These behavior have been covered for many years and even if some related case are not currently caught, the covered one should not be regressed. The next four changesets introduce tests for some of these cases. However we could produce many more tests cases since the area is wide and they are many possible combination. (And we should cover them when getting back to this issue) Since 5.5 is one week away, the most reasonable approach seems to back this out while we devise a new way to move forward that preserve the current behavior, catch more issues and also improves the situation that c26335fa4225 target. In addition to the behavior change, c26335fa4225 also introduced output changes. These output changes does not requires a backout per-se, but are part of the same changeset. However they come with a couple of issues that also requires attention: 1) the bulk of the error message have been shoehorned into a multiple line abort message. This seems quite different from what we usually do. The abort message should be a compact and efficient message, with extra details being issued as normal error output beforehand. (with --verbose/--quiet) support. 2) the current output is unbounded, so if there is many (tens, hundreds, thousands, …) of unstable/obsolete changeset involved in the push, the output can quickly become a scary and un-usuable wall of text. So we need some limitation here (same as we have with the remote head list that says A, B , C and # others).