Git push to drupal.org always returns "Everything up-to-date"
This not a real "answer" to the question I asked, but only the method I finally found to get out of my blocking situation.

Since it seemed not possible to make the remote repository to accept push attempts from its associated local repository, I took the problem from the opposite end.

After all it appears as a quite simple solution:


I renamed my local repository, say to myModule.old
I cloned the remote repository with
git clone --branch 7.x-1.x [myName]@git.drupal.org:project/myModule.git,
so getting a new myModule local repository
then I pasted whole contents from myModule.old into myModule, added and committed them
and finally used a simple git push origin (NOTE: without tag mentioned), with success


BTW, it's interesting to notice that trying with the tag mention again returned the "Everything up-to-date" message.
In the other hand, once pushed new contents, the myModule.info file displays normally rather than with the previous weird fashion.

Hope this helps somebody.