replicate ignores -config flag when database is specified

[mtlynch]

Example command

litestream replicate -config /home/mike/litestream.yml "${PWD}/data/store.db" s3://scratch.tinypilotkvm.com/db

For the command above, litestream silently ignores the -config flag, which caught me by surprise. The issue seems to be here:

https://github.com/benbjohnson/litestream/blob/f652186adf7470256b6a7bf7e96194dde49c2af2/cmd/litestream/replicate.go#L43L61

It only reads the config flag if it's the only argument, like:

litestream replicate -config /home/mike/litestream.yml

Desired behavior

If I've specified a -config file but litestream is not using it, I'd like litestream to error out or print a warning.

It'd also be handy if litestream allowed me to specify a db, and then if there's only one replica URL in my config file, it just uses that one, so I could say:

litestream replicate -config /home/mike/litestream.yml "${PWD}/data/store.db"

And then if my config file had an entry for store.db, litestream just picks the first replica URL.

[benbjohnson]

Yeah, that is not a great behavior. I'll have it error out if a config is specified but not used.

I'm a little hesitant about overloading the CLI args. Right now I see two use cases—one where someone is new to Litestream and just wants to try it out with a DB & replica URL and another where someone sets up a config and runs in production.

[benbjohnson]

This issue is fixed with #94. I added tests for all the commands in a runbook to verify they all work correctly. I can reopen the issue if you have any problems.