Allow specifying a different file to save CONVEX_DEPLOYMENT and VITE_CONVEX_URL to #206
Description
from #193 (comment)
maybe npx convex dev --env-file ../../.env should cause VITE_CONVEX_URL / NEXT_PUBLIC_CONVEX_URL / CONVEX_URL to be written to that file as well.
That's not what --env-file does today, so we need to make sure this makes sense / is backward compatible with this flag. Today this file is only used to read CONVEX_DEPLOYMENT or CONVEX_SELF_HOSTED_URL.
We could separate reading CONVEX_DEPLOYMENT / CONVEX_SELF_HOSTED_URL out (--env-file today) from writing VITE_CONVEX_URL (no option today, could be called --client-url-env-file). They're fundamentally two different things: VITE_CONVEX_URL is about publishing the location of the deployment to the client. CONVEX_DEPLOYMENT / CONVEX_SELF_HOSTED_URL are about telling the CLI which deployment to dev against / deploy to.
Note that {NEXT_PUBLIC_,VITE_,}CONVEX_URL will likely be joined by {NEXT_PUBLIC_,VITE_}CONVEX_SITE_URL soon.