Negation of search options

We currently have filters for author, mentions, attachments, dates and channels but it would be useful to add negation of search filters onto this.

My proposal is that as well as being able to specify a message meets a criterion you should be able to negate this and search through message history where a certain criterion is not met.

For example, I may do something like "from:joе#1337 lemons" to search for messages from myself about my favourite citrus, but it would be useful to be able to search "-from:joе#1337 lemons" to see my friends talking about the yellow coloured fruit and not include messages from myself.