Feature: kill notification with given tag

[adrianFD22]

The title. This would be great for scripting usage. I am currently using xnotify to send a "low battery" notification and with this feature I would be able to automatically remove the notification when pluging the charger. Thanks 4 the repo.

[adrianFD22]

I found a way more or less. I create a notification with the TAG I want to close and SEC:1. This solution closes the notification with one second of delay, pretty usable.

[phillbush]

One feature i had in mind to implement in XNotify is to add commands.
For example, if a notification line begins with, say, an exclamation point, it is interpreted as a command instructing XNotify what to do with the currently open notifications (such as close notifications with a given tag).
That feature would then replace the signal interface, which is clumsy and limited to two or three static operations without any argument or object to act upon.

That should be a major change on the interface. And the command syntax particularly should be simple but also extensible, with a handful set of commands.
I am going to think on possible commands (such as close, which can be parameterized by TAG or position of the notification on the queue) and on a syntax for them. Feel free to comment ideas on that in this issue.

[cdlscpmv]

@phillbush have your reached any conclusion on the idea?

If not, I would like to propose a simple interface but it would only work for closing notifications: if the user supplies an empty summary to xnotify while the tag is not empty, the notification with that tag is removed. Seems to be pretty consistent with how it works now.