Odd behavior with --dry-run and --upgrade

[Roel Janssen]

Dear Guix,

For some time now, running `guix package --dry-run --upgrade' results in
build actions involving grafting.  For a dry-run, I find that really
odd.  I believe the correct behavior should be what can be achieved
with: `guix package --dry-run --no-grafts --upgrade'.

Do you think the behavior of --dry-run should be changed to not graft
things by default?  And if so, do you have a pointer where I could find
the problematic code?  I couldn't find anything particularly odd because
the code involved has a `dry-run?' condition pretty much everywhere it
matters.

Kind regards,
Roel Janssen