Allow expanded variables for task conditions

Issue description

Conditional tasks do not allow for matching to result of a variable expansion. The match is done as plain text.

Example

1. Create a build variable called TEST_BRANCH
2. Add condition to plan:
   Variable planRepository.branch equals ${bamboo.TEST_BRANCH}
3. Save

Suggestion

Allow variable expansion for task conditions

Workaround

You can effectively add these conditions by using a Script task instead of the conditional task:

# only run git commands on specific "test branch"
if [[ ${bamboo.planRepository.branch} -eq ${bamboo.TEST_BRANCH} ]]; then
  # git commands
else
 echo "Skipping, condition not met";
fi

# only run git commands on specific "test branch"
if ($bamboo_planRepository_branch -eq $bamboo_TEST_BRANCH) {
  # git commands
} else {
  write-host "Skipping, condition not met"
}