Update pre commit hook doc in wiki

[chetanmeh]

Currently the wiki for contribution says the commit hook should be set like

$ cat /path/to/openwhisk/.git/hooks/pre-commit
#!/usr/bin/env bash
python /path/to/incubator-openwhisk-utilities/scancode/scanCode.py .

For me this was not stopping commits which changed build.gradle with no EOL. On checking with @csantanapr he suggested that commit hook should be something like

$ cat /path/to/openwhisk/.git/hooks/pre-commit
#!/usr/bin/env bash

# determine openwhisk base directory
root="$(git rev-parse --show-toplevel)"
python /path/to/incubator-openwhisk-utilities/scancode/scanCode.py . --config $root/tools/build/scanCode.cfg

As its not possible to open PR for wiki opening an issue for proposing the change

[csantanapr]

Wiki updated https://github.com/apache/incubator-openwhisk/wiki/Contributing:-Git-guidelines