I want to configure a tool so that I can just call with a movie as an argument and automatically download the appropriate english subtitle by file hash or name. I recall I had something configured like that but now I don’t remember what was the tool I used.
Maybe you are thinking of Subliminal which works by calling GuessIt to identify the video and then tries to find and download subtitles from various sources. There are plugins to use it automatically from mpv and probably other players too.
Edit: looks like most of the providers are broken so this doesn’t work very well anymore.