Use custom backtest config files

[xzmeng]

Is your feature request related to a problem? Please describe.
Currently we run freqtrade webserver with a fixed set of config files, which are then used for backtesting. If we need to use different config files, we must restart with updated command-line arguments. Could we introduce an option to specify config files dynamically when running backtests, eliminating the need for a restart ?

Describe the solution you'd like

1. Add a Custom config files option. When enabled, users can specify a list of config files.
2. Provide the ability to save the current combination of custom config files as a reusable template for covenience in future use.

[xmatthias]

users can specify a list of config files.

I'm not sure that'll be good from a usability point of view.
you'll have to assume a user 100% types it correctly (otherwise the command just fails as the bot won't fine the config).
You can't rely on the file being where you think it is (e.g. ../data/confignew.json) - so a directory listing won't help.

Provide the ability to save the current combination of custom config files as a reusable template for covenience in future use.

Not sure how to interpret this ... would you simply save something around this?

    "add_config_files": [
        "./partial_api.json",
        "./partial_telegram.json",
//...
    ],

---

I wonder what the point of this "really" is - like - what are you changing regularily between backtests that isn't in a the strategy?
the only thing jumping to mind is pairlist (might not be the only thing - but it's the most obvious).
I'd pretty much prefer having an option to configure necessary things instead - to me, that seems to be the simpler / more user-friendly method.

[xzmeng]

mainly pairlist, and some other configs, like trading mode

I've found add_config_files very useful just after creating this issue 👍

[xmatthias]

add_config_files was added first and foremost for my personal benefit.
Purely from what i'm working on, i use a ton of different configs for different tests - so being able to include the standard api config, telegram and exchange configs is a huge gain 😆