On Fri, Apr 13, 2018 at 10:14 AM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, Apr 13, 2018 at 12:02 AM, Elijah Newren <newren@xxxxxxxxx> wrote: >> However, it turns out we have this awesome function called >> "was_tracked(const char *path)" that was intended for answering this >> exact question. So, assuming was_tracked() isn't buggy, the correct >> patch for this problem would look like: > > Apparently that causes problems, for some odd reason. > > I like the notion of checking the index, but it's not clear that the > index is reliable in the presence of renames either. Yes, precisely. Checking the *current* index is not reliable in the presence of renames. Trying to use the current index as a proxy for what was in the index before the merge started is a problem. But we had a copy of the index before the merge started; we just discarded it at the end of unpack_trees(). We could keep it around instead. That would also have the benefits of making the was_dirty() checks more accurate too, as using the mtime's in the current index as a proxy for what was in the original index has the potential for the same kinds of problems. >> A big series >> including that patch was merged to master two days ago, but >> unfortunately that exact patch was the one that caused some >> impressively awful fireworks[1]. > > Yeah, so this code is fragile. > > How about we take a completely different approach? Instead of relying > on fragile (but clever) tests, why not rely on stupid brute force? > > Yeah, yeah, it's bad to be stupid, but sometimes simple and stupid > really does work. > <snip> > Comments? Because considering the problems this code has had, maybe > "stupid" really is the right approach... It's certainly tempting as an interim solution. I have an alternative interim solution that I think explains well why the code here had been fragile, and how to just implement what we want to know rather than making approximations to it, which I just posted at [2]. But I can see the draw of just gutting the code and replacing with simple brute force. Long term, I think the correct solution is still Junio's suggested rewrite[1]. My alternative is slightly closer to that end-state, so I favor it over simple brute-force, but if others have strong preferences here, I can be happy with either. Elijah [1] https://public-inbox.org/git/xmqqd147kpdm.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxx/ [2] https://public-inbox.org/git/20180413195607.18091-1-newren@xxxxxxxxx/
