Why is this Bash function within a git alias executing twice, and why does adding `exit` fix it?

Question

If I fail to explicitly call exit for certain function-based Bash scripts then there are additional unexpected executions for some functions. What is causing this? The behavior

Answer 1

The question has already been answered by gniourf_gniourf so I have created a version of the simplified alias/script which works as I originally intended. Since this is technically an answer and not really part of the question, I have added this as an answer. This answer supplements the other answer by gniourf_gniourf and is not intended to take credit away from his correct answer.

This fixed version of the simplified script either executes a found function or outputs nothing at all, and the fact that Git is placing $@ at the end of the script is corrected for by the addition of a comment at the end of the script. This is a fixed version of the simplified script (which gives the correct execution behavior of executing once):

g(){
    echo "once";
};

if [[ $(type -t "$1") == "function" ]];
then
$1;
fi;
#

Here is the output from this corrected version of the simplified alias/script (which has the correct behavior: execute once and display nothing for unknown input):

$git config --global alias.encrypt-for '!g(){ echo "once";};if [[ $(type -t "$1") == "function" ]];then $1; fi;#'
$ git encrypt-for g
once
$ git encrypt-for github
$ git encrypt-for facebook
$ exit

The bottom line is that because of the way Git handles aliases (see gniourf_gniourf's answer answer for an explanation of that) you must workaround the fact $@ will be suffixed to the end of your alias/script.