Add Replace from file to Replacement Editor

[dufferzafar]

We have a replacement editor (press o then R in mitmproxy) that allows us to add replacement patterns for flows.

There's also a --replace-from-file cmdline option that gets the replacement text from a local file.

But this functionality can't be used from the replacement editor itself.

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A user tried to enter the path to file in the Replacement text field: https://discourse.mitmproxy.org/t/emulate-charles-proxys-map-local/116

[arjunkaruvally]

Is anyone currently working on this issue ? If no, may I work on this ?

[dufferzafar]

@arjun23496 I don't think anyone is working so feel free to take it up, but before you start I think it'll be nice if you discuss your ideas with the dev team over at Slack.

[cortesi]

Fixed by #2120