git pull & git gc

Hello,

I have a local folder with the git-repository (so that its .git/config contains ([remote "origin"]\n url = git://github.com/git/git.git\nfetch = +refs/heads/*:refs/remotes/origin/* )

I do there "git pull".

Usually the output is
   Already up to date

but since today it prints
   Auto packing the repository in background for optimum performance.
   See "git help gc" for manual housekeeping.
   Already up-to-date.

and starts in the background a "git gc --auto" process. This is all fine, however, when the "git gc" process finishes, and I do again "git pull" I get the same message, as above (git gc is again started).

My understanding is, that "git gc" has to be occasionally run and then the garbage collection is done for a while. In the concrete case, if "git pull" starts "git gc" in the background and prints a message on this, it is all fine, but running "git pull" after a while, when the garbage collection was recently done, where shall be neither message nor an action about "git gc".

My system-wide gitconfig contains "[pack] threads = 1".

I have "tar xJf"'ed my local git repository and have put it under
   http://mail.aegee.org/dpa/v/git-repository.tar.xz

The question is:

Why does "git pull" every time when it is invoked today print information about "git gc"?

I have git 2.3.3 adjusted with "./configure --with-openssl --with-libpcre --with-curl --with-expat".

Thanks in advance for your answer

Dilian