Re: Properties of trees referencing commit objects (mode 160000)?

From: Jeff King <peff@peff.net>
Date: Mar 20, 2016, 04:18 UTC
Message-ID: <20160320041803.GC18312@sigill.intra.peff.net>
In-Reply-To: <20160319221348.GA5247@x>

On Sat, Mar 19, 2016 at 03:13:48PM -0700, Josh Triplett wrote:

Show 7 quoted lines

> I'm building some tools to track commit objects, and I'm thinking of
> using submodule-style references to commit objects in tree objects (mode
> 160000) to do so.  I'm trying to figure out some of the properties of
> that.
> 
> Can a commit object referenced that way live in the same repository,
> rather than some external repository?

Yes, it can be in the same repository, but...

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> Will git treat such a reference as keeping the commit object (and
> everything recursively referenced by it) live and reachable?  If that
> commit object is only reachable by the tree, and not by following the
> parents of any commit directly referenced from refs/*, will git discard
> it as unreachable?

No, we do not follow "gitlinks" like this for reachability. Neither for pruning, nor for object transfer via push/fetch. So you'd need to have a separate reference to it (or history containing it).

-Peff