dgit and git-dpm (was Re: Standardizing the layout of git packaging repositories)

[Ian Jackson <ijackson@chiark.greenend.org.uk>]

Brian May writes ("Re: Standardizing the layout of git packaging repositories"):
> However, with git-dpm, no branch is ever destroyed. Every branch is always
> merged into the Debian branch. The Debian branch itself always heads in a
> single forward direction and this branch is never rebased. Furthermore,
> because this is a pseudo-standard, everything can expect this is what will
> happen.
> 
> See http://git-dpm.alioth.debian.org/ for details.

I have an experimental version of dgit (not yet uploaded anywhere)
which handles .pc differently: the dgit git tree does not contain .pc.
I wrote some (frankly quite terrifying) code to reconstruct a .pc from
the artifacts available to dgit (mainly debian/patches and ../*orig*).

I used my new dgit to clone xwit (since that's listed as the example
in the git-dpm page) and the dgit git tree for 3.4-15 is almost
identical to that at the alioth tag debian-3.4-15.  There is one
difference: dgit's tree does not contain .gitignore.  I don't think
the lack of .gitignore is important for git-dpm users.  (Arguably it's
a bug that git-buildpackage et al remove it.)

Also, it appears that the successive git-dpm uploads in a suite are
fast-forwarding - usually, at least.  (I don't know if this is
enforced.)

I think what this means is that the git-dpm git branch is suitable,
directly, for use with `dgit push'.

If you use dgit to build and push from the git-dpm branch, your source
package will contain .gitignore (which is good, of course).  Another
developer who dgit clones your package will get your git-dpm history.

If they then NMU for a bugfix, they will make commits on the end of
your git-dpm history.  Does git-dpm's workflow easily permit the
incorporation of such a bugfix into the git-dpm history ?

I have one further question: is it possible, with git-dpm, to
construct a commit to build and upload from which (a) has the
commit and tree structure required for git-dpm, and (b) has an
arbitrary commit as an ancestor (somewhere) ?

If you are the maintainer and are using dgit, you will need to do that
operation when you are incorporating a non-dgit NMU.  Such an NMU will
be represented as an ad-hoc commit structure on the end of your
history.

Thanks,
Ian.