Upload API - skip upload, when file with the same content already uploaded

The Dropbox API doesn't offer a way to do this automatically, but I'll pass this along as a feature request. I can't promise if or when that might be implemented though.

You could effectively reproduce this behavior though, at least within an account. To do, you'd need to do something like this:

• Use /2/files/list_folder[/continue] to list the metadata for the contents of the account, which includes the 'content_hash' for each file. (You can cache this and update it over time as needed.)
• Before starting an upload of a file, compute the content hash of the local data.
• Check if that local content hash exists in the account already, by looking for it in the metadata retrieved in the first step.
• If the content_hash is found in the existing metadata, use /2/files/copy_v2 to copy the existing file to the new path instead of uploading it again. If it is not found, proceed to upload it normally (e.g., using UploadSessionStartAsync, etc.).