Motivation: gitaly is currently not in official backports because gitlab-common cannot migrate to testing. It cannot even be in fast track because dak is rejecting it. If we can get gitlab-common to testing that makes maintenance easier by allowing others to update it (currently only praveen can update it as it is in his personal repo).

Plan: It cannot go to gitaly binary because it will require an epoch for dak to accept the older version. But we can add it to gitlab-shell as it will soon have a bigger version than gitlab in unstable (11.8) and both gitlab and gitlay depends on it via gitlab-common.

Step 1: Add gitlab-common to gitlab-shell source package in a separate branch (gitlab-common branch) and remove gitlab-common from gitlab source package (in n-gitlab-common branch).

Step 2: Update gitlab's dependency on gitlab-shell from =${source:Version} to >= 11.8.10

Step 3: Release gitlab-shell with gitlab-common when gitlab-shell version is >> 11.8.10. If required create version like 11.8.11.REALLY.11.0.0 to avoid delay. Release gitlab without gitlab-common in unstable.

TODO: We have to test if older version in unstable has a higher priority over newer version in experimental.