If you have enabled git information in the shell prompt (like branch name, working tree status, etc.) , an upgrade to F18 breaks this functionality. What's worse, __git_ps1 (a shell function) isn't found, and a yum plugin goes looking for a matching package name to install, making running any command on the shell *very* slow.
A workaround, till the bug is fixed, is to do:
ln -s /usr/share/git-core/contrib/completion/git-prompt.sh /etc/profile.d/
Bug 878428, if you want to track progress.
 To add such git information in the shell display (for bash), add this to your .bashrc file:
export GIT_PS1_SHOWDIRTYSTATE=true export GIT_PS1_SHOWUNTRACKEDFILES=true export PS1='\[33[00;36m\]\u@\h\[33[00m\]:\[33[01;34m\] \w\[33[00m\]$(__git_ps1 " (%s)")\$ '