Staging dependencies that go into the snap

Is there an automation currently that snapcraft uses to determine what libraries to stage into the snap at build time?
For example, I am currently trying out permutations and combinations to snap atom, and

for the part definition in snapcraft.yaml , where I add the step

stage-packages , I just extracted the debian archive from atom’s downloads page,
and found some dependencies defined in control file which are as follows

Depends: git, gconf2, gconf-service, libgtk2.0-0, libudev0 | libudev1, libgcrypt11 | libgcrypt20, libnotify4, libxtst6, libnss3, python, gvfs-bin, xdg-utils, libcap2
Suggests: libsecret-1-0, gir1.2-gnomekeyring-1.0

I then went ahead and added all of them to stage-packages.

Note I am not / was not sure these are run-time dependencies, but assumed so

I know it is tough for even the most experienced software packager to guess dependencies,

but can package managers or snapcraft guess these dependencies, If a developer does not add

the stage-packages step to his snapcraft build?