Actually i was trying to publish more than 1 package repositories in the same aptly server, merging snapshots is cool but it was not actually the one that i want.
For example; I have one debian package repository to mirror and I want all of its components in the same published snapshot.
Taking snapshots for each component like this :
$ aptly snapshot create jessie-main-8.3 from mirror debian-main
$ aptly snapshot create jessie-contrib-8.3 from mirror debian-contrib
and so on...
And publish these snapshots in one :
$ aptly publish snapshot -component=main,contrib,non-free -distribution=jessie jessie-main-8.3 jessie-contrib-8.3 jessie-nonfree-8.3 my-debian
distribution prefix is so important if you want to publish another package repository in the same server so I could publish my jessie-security mirror snapshot
like this :
$ aptly publish snapshot -distribution=jessie jessie-security-8.3 my-debian-security
Thank you for your answers btw, I appreciate it.