what is fast-forwarding push in the Git?

Question

From the Git documentation:

By default, the configuration flag receive.denyNonFastForwards is enabled in shared repositories, so that you cannot force a non fast-forwarding push into it.

I know about the git push command, but what is fast-forwarding push?

Answer 1

Basically this means that you won't be re-writing commit history that already exists on your Git server (the already-pushed stuff).

If this history changes it could be a problem for others who have already pulled and worked off that history.

A manual way to determine if you are pushing "fast forward" is to look at what ref you have for your downloaded copy of your branches remote (let's say master):

git rev-parse origin/master #returns sha

Then, download the content from your remote server and check again:

git fetch
git rev-parse origin/master #returns sha

If the return result of those those two rev-parse commands are equal your push will be fast-forward.

BUT...all that work really isn't necessary. Just simply pull before you push and you will be good.

git pull origin master
# resolve any conflicts
git push origin master