It is possible to upgrade easily from 6.2 > the latest stable version? Seems like you cannot skip versions, and have to upgrade as 6.3 > 6.4 > 6.5 etc..
This seems like a massive task!
We considered installing a separate VM with the latest version on running alongside, and cloning repo > new repo.
You can certainly skip most versions. Though there are only documented steps for certain jumps. You should be fine in your case though.
For source installs: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/update/6.x-or-7.x-to-7.14.md
Once you have updated to the 7.14 you can switch to using the omnibus packages to make upgrading easier going forward: https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/doc/update/README.md#upgrading-from-a-non-omnibus-installation-to-an-omnibus-installation
And then you will be able to upgrade to the latest stable which is 8.0.
Alternatively if you want to stick with the source install you can do the following after getting to 7.14: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/update/7.14-to-8.0.md
