dependency issue with groups

[jp-embedded]

In the attached project, in file project/Tupfile:

a.c | ../submodules/sm1/<lib> ../submodules/sm2/<lib> |> gcc %f %<lib> -o %o |> gr2                                                
a.c | ../submodules/sm1/foo.o ../submodules/sm2/bar.o |> gcc %f %i -o %o |> gr3

If "../submodules/sm2/bar.o" is removed as dependency, gr3 is rebuild
If "../submodules/sm2/bar.o" is re-added as dependency, gr3 is rebuild
If "./submodules/sm2/<lib>" is removed as dependency, gr2 is rebuild
If "./submodules/sm2/<lib>" is re-added as dependency, gr2 is NOT rebuild

tup-test-groups.tar.gz