Re: [PATCH 4/6] init: make a copy of $GIT_DIR string

> We pass the result of getenv("GIT_DIR") to init_db() and assume that the
> string remains valid. But that's not guaranteed across calls to setenv()
> or even getenv(), although it often works in practice. Let's make a copy
> of the string so that we follow the rules.
>
> Note that we need to mark it with UNLEAK(), since the value persists
> until the end of program (but we have no opportunity to free it).