fix: Fix basher PATH redundancy on shell-reload

[chetanc10]

Tested for bash only, though it should be applicable for other 'simple' shells but NOT fish.

Before this patch, every shell session reload redundantly updates $PATH:

root@b888df0f96a7:/# echo $PATH | grep "\.basher/bin"
/root/.basher/cellar/bin:/root/.basher/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
root@b888df0f96a7:/# exec bash -l
root@b888df0f96a7:/# echo $PATH | grep "\.basher/bin"
/root/.basher/bin:/root/.basher/cellar/bin:/root/.basher/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
root@b888df0f96a7:/# exec bash -l
root@b888df0f96a7:/# echo $PATH | grep "\.basher/bin"
/root/.basher/bin:/root/.basher/bin:/root/.basher/cellar/bin:/root/.basher/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

After this patch, PATH is not redundantly updated for every shell reload:

root@b888df0f96a7:/# exec bash -l
root@b888df0f96a7:/# echo $PATH | grep "$HOME/.basher/bin"
/root/.basher/cellar/bin:/root/.basher/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
root@b888df0f96a7:/# exec bash -l
root@b888df0f96a7:/# echo $PATH | grep "$HOME/.basher/bin"
/root/.basher/cellar/bin:/root/.basher/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

[juanibiapina]

Thanks for the contribution. How about adding a test for this?

[chetanc10]

Unable to find proper way to add test for install.sh so far as it's not run in controlled environment like basher test cases.

Will check and update.