ci: add working-directory test

[guitarrapc]

Add test for #58 issue (PR: #59)

[guitarrapc]

confirm test failed. let's merge master to confirm issue fixed.

[guitarrapc]

failed reason is $CIRCLE_WORKING_DIRECTORY seems expand to ~ when working_directory not specified.

Cloning git repository
+ existing_repo=false
+ mkdir -p '~/test-working-directory/.'
+ cd '~/test-working-directory/.'
+ git clone --depth 1 git@github.com:guitarrapc/git-shallow-clone-orb.git .

Require realpath or similar solution?

use Shell Expantion is valid for bash, but not for sh.

foo="~"
echo ${foo/#\~/$HOME}

[guitarrapc]

Wait till GitHub recover from PR degrade status.

[guitarrapc]

ok, all test passed.