Sources a custom install location twice

[ches]

Hi,

When a custom install location is given to install.py, it modifies autojump.sh erroneously: it appends a new if block at the end of the file, when it should instead include another elif so that it does not potentially source the main shell file twice in case a distribution symlinks it into a standard location.

On a default Homebrew installation using /usr/local prefix, this is the resulting autojump.sh symlinked at /usr/local/etc/profile.d/autojump.sh after installation:

# the login $SHELL isn't always the one used
# NOTE: problems might occur if /bin/sh is symlinked to /bin/bash
if [ -n "${BASH}" ]; then
    shell="bash"
elif [ -n "${ZSH_NAME}" ]; then
    shell="zsh"
elif [ -n "${__fish_datadir}" ]; then
    shell="fish"
elif [ -n "${version}" ]; then
    shell="tcsh"
else
    shell=$(echo ${SHELL} | awk -F/ '{ print $NF }')
fi

# prevent circular loop for sh shells
if [ "${shell}" = "sh" ]; then
    return 0

# check local install
elif [ -s ~/.autojump/share/autojump/autojump.${shell} ]; then
    source ~/.autojump/share/autojump/autojump.${shell}

# check global install
elif [ -s /usr/local/share/autojump/autojump.${shell} ]; then
    source /usr/local/share/autojump/autojump.${shell}
fi

# check custom install
if [ -s /usr/local/Cellar/autojump/22.5.3/share/autojump/autojump.${shell} ]; then
    source /usr/local/Cellar/autojump/22.5.3/share/autojump/autojump.${shell}
fi

The Homebrew installation does create symlinks at /usr/local/share/autojump/autojump.${shell}, so because the "check custom install" block is not an elif, it sources twice and essentially doubles autojump's load time in shell startup.