gclient sync ... Cannot fast-forward merge, attempt to rebase? (y)es / (q)uit / (s)kip

Here is the workaround solution for the problem:

4) gclient sync

Syncing projects:   2% ( 2/84) src-internal

src-internal (ERROR)
----------------------------------------
[0:00:01] Started.
_____ src-internal at refs/remotes/origin/master
[0:00:05] Cannot fast-forward merge, attempt to rebase? (y)es / (q)uit / (s)kip :

Just push your changes to remote repo.

Seriously. Somehow gclient corectly resolves dependencies when pulling DEPS from remote.