Create a Netlify deploy via the REST API with the file-digest method (upload only changed files)

Documented steps

1. Compute the SHA1 of every file in the publish directory and build a digest: {"files": {"/index.html": "<sha1>", ...}}. To include serverless functions, add a "functions" object mapping function names to their SHA1s.
2. POST the digest to https://api.netlify.com/api/v1/sites/{site_id}/deploys with 'Authorization: Bearer <TOKEN>' and 'Content-Type: application/json'. For large deploys add "async": true to the body and poll the deploy until it is ready for uploads.
3. The response contains the deploy 'id' plus 'required' (a list of SHA1 sums Netlify does not yet have — not file paths) and 'required_functions'. Map each required SHA1 back to your local paths; identical files share one SHA1 and need only one upload.
4. Upload each required file with PUT https://api.netlify.com/api/v1/deploys/{deploy_id}/files/{path} using 'Content-Type: application/octet-stream' and the raw file bytes as the body (URL-encode the path).
5. Upload each required function with PUT https://api.netlify.com/api/v1/deploys/{deploy_id}/functions/{name}?runtime=js (runtime js or go). Zip the function bundle before uploading — the endpoint expects a zipped function.
6. Poll GET https://api.netlify.com/api/v1/deploys/{deploy_id} until 'state' is 'ready' (or 'error'). When ready, the deploy is live on the CDN.
7. Docs: https://docs.netlify.com/api-and-cli-guides/api-guides/get-started-with-api/