From: Jeff King <peff@peff.net>
Date: Tue, 03 Apr 2018 18:28:00 GMT
Subject: Re: [PATCH 2/6] commit: add generation number to struct commmit
Message-ID: <20180403182800.GA8377@sigill.intra.peff.net>
In-Reply-To: <20180403180536.GB100220@google.com>

On Tue, Apr 03, 2018 at 11:05:36AM -0700, Brandon Williams wrote:

> On 04/03, Derrick Stolee wrote:
> > The generation number of a commit is defined recursively as follows:
> > 
> > * If a commit A has no parents, then the generation number of A is one.
> > * If a commit A has parents, then the generation number of A is one
> >   more than the maximum generation number among the parents of A.
> > 
> > Add a uint32_t generation field to struct commit so we can pass this
> 
> Is there any reason to believe this would be too small of a value in the
> future?  Or is a 32 bit unsigned good enough?

The linux kernel took ~10 years to produce 500k commits. Even assuming
those were all linear (and they're not), that gives us ~80,000 years of
leeway. So even if the pace of development speeds up or we have a
quicker project, it still seems we have a pretty reasonable safety
margin.

-Peff