On Fri, Jun 1, 2018 at 10:03 PM, Duy Nguyen <pclo...@gmail.com> wrote: > On Fri, Jun 1, 2018 at 8:34 PM, Elijah Newren <new...@gmail.com> wrote: >> On Fri, Jun 1, 2018 at 9:11 AM, Nguyễn Thái Ngọc Duy <pclo...@gmail.com> >> wrote: >>> This is more of a bug report than an actual fix because I'm not sure >>> if "o->src_index" is always the correct answer instead of "the_index" >>> here. But this is very similar to 7db118303a (unpack_trees: fix >>> breakage when o->src_index != o->dst_index - 2018-04-23) and could >>> potentially break things again...
I'm pretty sure your patch is correct. Adding Brandon Williams to the cc for comment since his patches came up in the analysis below... >> Actually, I don't think the patch will break anything in the current >> code. Currently, all callers of unpack_trees() (even merge recursive >> which uses different src_index and dst_index now) set src_index = >> &the_index. So, these changes should continue to work as before (with >> a minor possible exception of merge-recursive calling into other >> functions from unpack-trees.c after unpack_trees() has finished..). >> That's not to say that your patch is bug free, just that I think any >> bugs shouldn't be triggerable from the current codebase. > > Ah.. I thought merge-recursive would do fancier things and used some > temporary index. Good to know. Well, it does does use a temporary index, but for dst_index rather than src_index. It then does some fancier things, but not until the call to unpack_trees() is over. In particular, at that point, it swaps the_index and tmp_index, reversing their roles so that now tmp_index is the original index and the_index becomes the result after unpack_trees() is run. That's done because I later want to use the original index for calling verify_uptodate(). verify_uptodate() is then used for was_tracked_and_matches() and was_tracked(). Anyway, the whole upshot of this is: * merge-recursive uses src_index == &the_index for the unpack_trees() call. * merge-recursive uses src_index == o->orig_index for subsequent calls to verify_uptodate(), but verify_uptodate() doesn't call into any of the sites you have modified. Further: * Every other existing caller of unpack-trees in the code sets src_index == &the_index, so this won't break any of them. * There are only two callers in the codebase that set dst_index to something other than &the_index -- diff-lib.c (which sets it to NULL) and merge-recursive (which does the stuff described above). So, having done that analysis, I am now pretty convinced your patch won't break anything. That's one half... >> Also, if any of the changes you made are wrong, what was there before >> was also clearly wrong. So I think we're at least no worse off. >> >> But, I agree, it's not easy to verify what the correct thing should be >> in all cases. I'll try to take a closer look in the next couple days. > > Thanks. I will also stare at this code some more in the next couple > days trying to remember what these functions do. Your patch has two divisible parts: 1) Your modifications to * clear_ce_flags_1() * clear_ce_flags_dir() * clear_ce_flags() * mark_new_skip_worktree() The clear_ce_flags*() functions are only called by each other and by mark_new_skip_worktree(), which in turn is only called from unpack_trees(). Also, in all of these, your change ends up only modifying what index_state is passed to is_excluded_from_list(). 2) Your modifications to * verify_clean_subdirectory() * check_ok_to_remove() In this case, the former is only called by the latter, and the latter ends up only being called (via verify_absent_1()) from verify_absent() and verify_absent_sparse(). I'll address each, in reverse order. 2) The stuff that affects verify_absent() While verify_absent() is not called from merge-recursive right now, it was something I wanted to use in the future for very similar reasons that verify_uptodate() started being called directly from merge-recursive. In particular, if the rewrite of merge-recursive[A] I want to do sets index_only when calling unpack_trees(), then does the whole merge without touching the worktree, then at the end goes to update the working tree, it will need to do extra checks. verify_absent() will come in handy as one of those extra checks. For that case, using the_index (the new index just created with lots of changes) would be wrong in all the same ways that using the_index caused massive problems for was_tracked() in merge-recursive (e.g. the blow up of when Junio merged the original directory rename detection series into master and subsequently reverted it); we'd instead want src_index (which was the index that existed when merge was called) instead. So, with this patch you've fixed some important bugs that I would have hit later. [A] sidenote: see https://public-inbox.org/git/xmqqk1ydkbx0....@gitster.mtv.corp.google.com/ for more details 1) mark_new_skip_worktree() ... is_excluded_from_list(). Sadly, I'm not very familiar with the skip_worktree and sparse checkout stuff. However, the fact that mark_new_skip_worktree() explicitly takes an index_state (and a different one is passed to it the two different times it is called), and that it is the only caller of the clear_ce_flags*() family of functions, and that those function use the cache entries from the index passed to them in all cases other than the calls to is_excluded_from_list() makes those two look like oversights. In fact, a little more digging turns up commit fba92be8f7 ("dir: convert is_excluded_from_list to take an index", 2017-05-05) and before then, those functions didn't use the_index directly. But they did use it indirectly, because they called a function in dir.c that had it hardcoded. So it looks like Brandon fixed part of the bug for us, but moved the incorrect hardcoding from dir.c to unpack-trees.c. Your patch is just fixing it up. In fact, a little more digging turns up: 2c1eb10454 ("dir: convert read_directory to take an index", 2017-05-05) a0bba65b10 ("dir: convert is_excluded to take an index", 2017-05-05) which appear to be the culprits behind the other two uses of the_index called from verify_absent(). It looks like before these commits that unpack_trees() was carefully using the appropriate index, except that functions in dir.c had use of the_index hardcoded. Brandon fix the functions in dir.c for us, but ended up still hardcoding the_index in unpack-trees.c. Basically, he did most of the necessary lifting, and your patch just finally changes them over to use the correct index. Brandon: Does anything look off in my analysis above?
