Re: [Gnu-arch-users] a brief note on "delta compression"

[Tom Lord]

    > From: Aaron Bentley <address@hidden>

    > Tom Lord wrote:
    > > * "delta compression" -- meaning "store pre-combined deltas"

    > > The second meaning of "delta compression" is vaguer, but generally
    > > refers to replacing a sequence of deltas (aka changesets), which are
    > > meant to be applied sequentially, with a single changeset that
    > > represents their composition.

    > This is the same as "summary deltas", discussed here:
    > http://mail.gnu.org/archive/html/gnu-arch-users/2003-09/msg01774.html

    > Summary deltas could be produced by "changeset composition":
    > http://mail.gnu.org/archive/html/gnu-arch-users/2004-01/msg01168.html

    > Right?

(I haven't double checked your URLs but) yes, this is pretty much the
same as what we've been calling "summary deltas" and I think that's a
better name for the idea than "delta compression".  To my ear, "delta
compression" is the right name for the first meaning I gave -- storing
revisions as deltas against other revisions.

If you want to split hairs, I guess you could conceive of compressed
(i.e., combined) deltas in a situation where you're throwing away the
intermediate history  -- "summary deltas" wouldn't be a good name for
that.   So there's maybe a very slight distinction between compressed
(combined) deltas in general and summary deltas in particular.   I
don't think you'd ever want combined deltas (in an archive) unless
they were summary deltas, though.

-t