Allow some form of robust templating

[patcon]

Handlebar is a templating library that allows simple logic. It might be nice to use it to allow for more robust templating for certain types of messages/strings.

One benefit of this is that comprehensive format rules could be set at General level, rather than setting them at each gateway.

Places to implement:

• RemoteNickFormat. Could allow for setting certain format based on protocol or.
• messages that are unthreaded, re: Hint at thread replies when messages are unthreaded #557
• message edits that can't be in-place, re: [Slack] Clarify context when a msg edit creates a new msg #588 (comment)
• translated messages, re: [WIP] Add Google Translation ability #512
• InitialComment template, re: Make sure threaded files stay in thread (slack). Fixes #590 #606 (comment)

Seems the best library in go: https://github.com/aymerick/raymond

[patcon]

We could perhaps also use custom helpers to do away with config like "StripNick", as people could do that via templates: https://github.com/aymerick/raymond#helpers

[patcon]

Potential use-cases:

• Allow special avatar for system user.
• Allow messages to have quick-access permalink to original message if they're on the same team, for example, during translation.
• Append "thread reply: " prefix if parent message is unthreaded.

[patcon]

Defaults here would be helpful, so might be nice to have a more robust default process, rather than simply empty strings or falsey values

[patcon]

Not sure whether mustache is the most appropriate engine, so generalizing this issue

[qaisjp]

Go has a text templating system in its standard library: text/template.

[patcon]

Thanks @qaisjp! text/template's looping doesn't feel very friendly to the vast number of people more familiar with non-golang template engines -- and feels like templates would be very user-facing :)

[42wim]

I think using tengo is the solution for this instead of templating, much more powerful

[patcon]

Good call. Closing out :) Thanks!