Improve support of directory names with spaces and POSIX compatibility

[ddddavidmartin]

Thank you very much for your input! Robustness against whitespaces has been lacking for quite a while in those scripts and I did not get a chance yet to have a look into it.

I will double-check your changes on my machine and merge your request then.

[emdroid]

Sorry, I pressed a wrong button and closed the pull request by accident :)

[emdroid]

I did some tests on my Linux machine, and I found some additional issues, created 2 new commits in the pull request to address those:

• support of path names starting with the "-" character (to prevent to be interpreted as an unknown option of the commands)
• the scripts use bash features (e.g. "source", "pushd", "function") but do actually specify /bin/sh as the command line interpreter; /bin/sh can (and usually does) point to a different interpreter than bash, so the script would not work then

[emdroid]

I did some more extensive testing on Linux, with an actual testing repository containing spaces and dash at the beginning, so I updated the pull request with the new commits which are working for me on the Linux box.

I also took the time to make the scripts POSIX compatible, i.e. instead of changing the shell line to always use /bin/bash, the scripts should now work with any POSIX compatible /bin/sh (tested with /bin/dash and /bin/ash on Ubuntu).

[ddddavidmartin]

Awesome, I really appreciate your efforts! I had a look over the changes and gave it a quick go on my Mac and it all seems to work fine (including whitespaces and everything). Big thumbs up for the POSIX compatibility as well!

I will close and merge this then. Thanks very much!