index: don't include nullid in len() I suspect the reason the nullid is in the index in the last position is that it lets index[i] for regular revision number, even when index was just a regular Python list. An alternative solution would have been to reserve revision number 0 for the null revision. I don't know why that wasn't done. Now that we have classes backing the index, we can easily make index[-1] get the nullid without having to put it last in the list and including it in the len(). This patch just hides the nullid -- it will still be accessible at index[len(index)]. I realize that this will be annoying when checking out across this commit for debugging (including bisection). Differential Revision: https://phab.mercurial-scm.org/D4022

index: replace insert(-1, e) method by append(e) method I want to make index[len(index) - 1] be the tip revision, not null revision as it is today. insert(-1, e) will then make little sense. Since insert() currently requires the first argument to be -1, it seems simpler to replace it by a method that allows insertion only at the end. Note that revlogoldindex already has this method (by virtue of extending list). Differential Revision: https://phab.mercurial-scm.org/D4021

pure: create type for revlog v0 index The new type takes care of hiding the nullid entry. This type helps us transition away from including that entry at index[len(index)-1]. Differential Revision: https://phab.mercurial-scm.org/D4020

index: drop support for negative indexes into the index I want index[i] to work for any valid revnum including -1 (as it already does), and I also want len(index) to be the number of revisions in the index (not counting the null revision), so it cannot also support negative revision numbers other than -1 for nullid. I didn't bother removing support for it from revlog v0. Differential Revision: https://phab.mercurial-scm.org/D4019