In gitmanager.py, function merge_pull_request(), on line 329:
return "Merged pull request [#{0}](github.com{1}/pull/{0})."
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In chatcommands.py, function approve(), on line 502:
message = GitManager.merge_pull_request(pr_id, comment)
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on line 517:
return message
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Therefore I think one should receive a message "Merged pull request ..." when running !!/approve?