"Raymond E. Pasco" <ray@xxxxxxxxxxxx> writes: > On Thu Aug 20, 2020 at 7:57 PM EDT, Junio C Hamano wrote: >> I do not see why we want to stress the last part after ", even if". >> The safety mechanism insists on the working tree file and the index >> entry to be identical, and the location where in the file the >> difference is, is irrelevant, whether it is outside the area the >> incoming patch touches, or it overlaps. > > It's because this is the confusing part of the option - it's easy to > grasp "apply the patch to both the working copy and the index", but > that's not exactly what the option does, it applies only in the case of > identical preimages (and therefore, identical postimages). That's fair. Back when "git apply" was introduced, workflows to create partial commits with "edit file; git add file; edit file; git commit" did exist, but the safety certainly far predates the more aggressive form of partial commits created by "add -p", "checkout -p", etc. (which is natural, as "add -p" and friends have to use "apply" as their implementation detail). As "git apply --index" was created primarily for preparing the index immediately followed by "git commit" (as an implementation detail for "git applymbox", which was "git am"'s precursor), it was one of the most obvious ways to avoid the situation where _your_ work in progress in the working tree and in the index gets mixed in the resulting commit made by applying other's patch to insist that the index and the working tree contents to match. As you suggest, of course, if the user deliberately wants to keep the index and the working tree to be different (e.g. changes in the working tree wrt the index are outside the block of text that is touched by any incoming patch), it is easy to bypass the safety feature by applying to the index and to the working tree separately, or just apply to the working tree and run another "add -p". Having said that, I still think the half-sentence after "even if" was of little value. If we want to give the reason why, "even if the patch may independently apply to the two, the two must be identical" doesn't at all. It complains that the description does not explain why the two must be identical without addressing the complaint the sentence itself raises. And if we are not going to give why that must be so, "the index and the working tree file must be identical" is much clearer without the "even if" part.
