dirstate-v2: Store unsigned integers inside DirstateEntry The negative marker values are not used anymore. Differential Revision: https://phab.mercurial-scm.org/D11634

dirstate-v2: Truncate directory mtimes to 31 bits of seconds … instead of 64 bits, while keeping the sub-second presision. This brings the size of one timestamp from 12 bytes to 8 bytes. 31 bits is chosen instead of 32 because that’s already what happens for the mtime of files and symlinks, because dirstate-v1 uses negative i32 values as markers. Later we’ll add sub-second precision for file/symlink mtimes, making their dirstate-v2 representation the same as for directories. Differential Revision: https://phab.mercurial-scm.org/D11633

dirstate-v2: Separate Rust structs for Timestamp and PackedTimestamp PackedTimestamp is now exclusively for dirstate-v2 serialization purpose. It contains unaligned big-endian integers. Timestamp is used everywhere else and contains native Rust integers. Differential Revision: https://phab.mercurial-scm.org/D11632

dirstate-v2: Change the representation of negative directory mtime Change it from how I previously thought C’s `timespec` works to how it actually works. The previous behavior was also buggy for timestamps strictly before the epoch but less than one second away from it, because two’s complement does not distinguish negative zero from positive zero. Differential Revision: https://phab.mercurial-scm.org/D11629