Kevin J. McCarthy authored
When viewing attachments externally with a (non-copiousoutput) mailcap entry missing %s, the command is invoked as a filter, with the attachment piped into stdin. However, unlike a filter, the user interacts with the command, instead of just displaying the output in the pager. Just as with the mutt_system() command, Mutt needs to send imap keepalives to keep those connections from closing during the potentially extended invocation. Thanks to John Hawkinson for the bug report, and his suggested patch, which this commit is based upon.