Support FastCGI for `caddy reverse-proxy`

[jtdowney]

Issue Details

I have a use case where it would be helpful to have a FastCGI flag when using caddy reverse-proxy instead of having to write a Caddyfile. It could be --transport fastcgi and keep the upstream --to. I'm happy to open a PR and want to confirm it's welcome before I proceed.

Assistance Disclosure

AI not used

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No response

[steadytao]

I would be open to considering a narrow PR for --transport http|fastcgi with http remaining the default.

I’d prefer this only selects the FastCGI reverse proxy transport and does not grow into a CLI replacement for php_fastcgi or the full Caddyfile transport config. Things like root, split_path, env, try_files, etc. should stay in the Caddyfile.

The PR should also define how --insecure and http:// / https:// schemes behave with FastCGI, most likely by rejecting invalid combinations of each.

[francislavoie]

FYI you could do a silly one-liner like this:

echo -e ":8888 {\n root ./public \n reverse_proxy localhost:9000 { \n transport fastcgi \n } \n }" | caddy run -c- -a caddyfile

You don't necessarily need to have a file on disk, but this gives you full flexibility.