GeezerVison

The 7-bit size groups in pack object headers, pack-like loose object headers and delta headers are shifted into place without checking whether bits fall off the top. The existing checks (including the one from #7172) only stop once the shift reaches the width of the type, so the last group can still lose its high bits and a size that doesn't fit is accepted as a smaller one. For example, the delta header 90 80 80 80 80 80 80 80 80 02 decodes to 16 on 64-bit platforms, because the 0x02 at shift 63 is dropped.

This checks that each group survives the shift and fails otherwise, like git's st_left_shift(). In parse_header_packlike() the group is an unsigned long, so on Windows it was also shifted by up to 60 bits on a 32-bit type; it is now shifted as a size_t.

Tests cover the delta base and result sizes, a pack-like loose object read through git_odb_read(), git_odb_read_header() and git_odb_open_rstream(), and a pack header through the indexer. The pack test only fails without the fix where long is 64 bits; on Windows the existing bitsizeof(long) check already rejects that header.