gitfunctions.sh should be Zsh compliant

The gitfa Shell function fails under Zsh.

In Zsh, the result of parameter substitution is not split into words (it's a feature, not a bug).
Solutions to have the common sh behavior are:

• setopt shwordsplit
• setopt rcexpandparam
• use an array
• use an alias

Also, the for loop does not split on line returns (\n), only on spaces.