Re: [PATCH v3 3/4] revision: avoid loading object headers multiple times

Patrick Steinhardt [off-list ref] writes:

When loading references, we try to optimize loading of commits by using
the commit graph. To do so, we first need to determine whether the
object actually is a commit or not, which is why we always execute
`oid_object_info()` first. Like this, we'll unpack the object header of
each object first.

This pattern can be quite inefficient in case many references point to
the same commit: if the object didn't end up in the cached objects, then
we'll repeatedly unpack the same object header, even if we've already
seen the object before.
...
Assuming that in almost all repositories, most references will point to
either a tag or a commit, we'd have a modest increase in memory
consumption of about 12.5% here.

I wonder if we can also say almost all repositories, the majority of
refs point at the same object.  If that holds, this would certainly
be a win, but otherwise, it is not so clear.