lazymanifest: avoid reading uninitialized memory I got errors running tests with clang UBSAN [1] enabled. One of them is: ``` --- test-dirstate.t +++ test-dirstate.t.err @@ -85,9 +85,115 @@ $ echo "[extensions]" >> .hg/hgrc $ echo "dirstateex=../dirstateexception.py" >> .hg/hgrc $ hg up 0 - abort: simulated error while recording dirstateupdates - [255] + mercurial/cext/manifest.c:781:13: runtime error: load of value 190, which is not a valid value for type 'bool' + #0 0x7f668a8cf748 in lazymanifest_diff mercurial/cext/manifest.c:781 + #1 0x7f6692fc1dc4 in call_function Python-2.7.11/Python/ceval.c:4350 + ....... + SUMMARY: UndefinedBehaviorSanitizer: invalid-bool-load mercurial/cext/manifest.c:781:13 in + [1] $ hg log -r . -T '{rev}\n' 1 $ hg status - ? a ``` While the code is not technically wrong, but switching the condition would make clang UBSAN happy. So let's do it. The uninitialized memory could come from, for example, `lazymanifest_copy` allocates `self->maxlines` items but only writes the first `self->lines` items. [1]: https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html Test Plan: Run `test-dirstate.t` with UBSAN and it no longer reports the issue. Differential Revision: https://phab.mercurial-scm.org/D1948