automatic dependency generation for << ${source:Next-Upstream-Version}

[Joachim Reichel <joachim.reichel@gmx.de>]

Hi,

(see #657720 for the background details and rationale)

to one of my binary packages I want to add a dependency like
Depends: foo (>= ${source:Upstream-Version}), foo (<<
${source:Next-Upstream-Version})

The question: how to achieve that given that
${source:Next-Upstream-Version} does not exist (and is not trivial to
compute in general)? I want to avoid hard-coding the next upstream
version because then the package is uninstallable whenever a new
upstream version of foo is uploaded (which is not bad in this specific
context, but it requires a sourceful change for the next upload).

I suppose "foo (= ${source:Upstream-Version})" does not work because it
will never match for non-native packages, right? Is there something like
"foo (upstream version of foo = ${source:Upstream-Version})"

I guess this can be implemented using debian/substvars. But I don't want
to reinvent the wheel. I'm probably not the first one with this problem.
Are there any examples how to do that easily?

Joachim