--local For writing options: write to the repository .git/config file. This is the default behavior. For reading options: read only from the repository .git/config rather than from all available files. See also the section called “FILES”.
--global For writing options: write to global ~/.gitconfig file rather than the repository .git/config, write to $XDG_CONFIG_HOME/git/config file if this file exists and the ~/.gitconfig file doesn’t. For reading options: read only from global ~/.gitconfig and from $XDG_CONFIG_HOME/git/config rather than from all available files. See also the section called “FILES”.
--system For writing options: write to system-wide $(prefix)/etc/gitconfig rather than the repository .git/config. For reading options: read only from system-wide $(prefix)/etc/gitconfig rather than from all available files. See also the section called “FILES”.