Improve sync-fork script

[teobais]

There is currently the assumption that the parent remote is named as upstream and the fork as origin. If the latter condition is not met, the script will fail.

Hence, there should be a condition which makes the script to smartly handle erroneous cases, so that the script always succeeds.

Logic is: if upstream contains my-github-username , swap upstream with origin.

Reference links

• http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-6.html
• http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-5.html