Re: [PATCH 3/6] Stop producing index version 2

Nguyễn Thái Ngọc Duy  [off-list ref] writes:

read-cache.c learned to produce version 2 or 3 depending on whether
extended cache entries exist in 06aaaa0 (Extend index to save more flags
- 2008-10-01), first released in 1.6.1. The purpose is to keep
compatibility with older git. It's been more than three years since
then and git has reached 1.7.9. Drop support for older git.

Cc'ing this, as I suspect this would surely raise eyebrows of some people
who wanted to get rid of the version 3 format.