Re: [PATCH v4 00/18] Extending the shelf-life of "git describe" output

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 3, 2012, 20:21 UTC
Message-ID: <7vtxxotx2n.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20120703193410.GA20503@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

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> What happens if I set multiple flags? One or more of them will be
> ignored (you _could_ try to establish a hierarchy, for example that
> TREEISH is a superset of COMMITISH, but that could not handle the *_only
> cases, which really are mutually exclusive). IOW, I think these are not
> really flags but rather enum elements.

Yes, I was aware of that. I counted five useful ones (see the new ones near the tip of 'pu') but there may be others, so you cannot fit in 2 bits and would need 3 bits.

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> It is probably an OK trade-off since we are also stuffing true flags
> like GET_SHA1_QUIETLY in the same field, and we don't want to make the
> parameter list too unwieldy by splitting out the enum. But it might be
> worth throwing a comment into cache.h that a certain set of the flags
> are mutually exclusive. Or I guess you could mask off that part and make
> sure only one bit was set, which would catch the error at run-time. But
> I think a comment is probably sufficient.

I actually am thinking to move these bit assignments backto sha1_name.c and make them private, as get_sha1_tree() and friends are easier to understand public interface functions than get_sha1_typish(... I_WANT_COMMIT|I_WANT_COMMITTISH|...).