RFE: add --ignore-status label/filter

[manics]

Allow PRs to be included regardless of their travis status by adding a new label/filter.

[sbesson]

I would have expected scc merge -S none to work for this. Can you expand on the type of scenario that you are looking into?

[manics]

-S none will merge all PRs regardless of status, the idea here is to allow individual PRs to be whitelisted, for example so that multiple dependent PRs can be included in a daily merge-all-PRs build without having to add workarounds in each PR to get Travis to pass.

[sbesson]

Understood. For PR-specific behavior, some detection logic would need to be inserted before:

scc/scc/git.py

Lines 988 to 990 in 81babbc

	status = pullrequest.get_last_status("base")
	if status is None:

to compare the labels and/or using the PullRequest.parse() API if we want to allow the status to be ignored via description/comment:

scc/scc/git.py

Lines 949 to 951 in 81babbc

	if pullrequest.parse(filters["exclude"].get("label"),
	whitelist=is_whitelisted_comment):
	return False, 'exclude comment'