Function sync_state 

pub fn sync_state(
    current: Option<ServerFile<'_>>,
    history: &[(i32, &str)],
    local_sha256: Option<&str>,
    base: Option<&BaseVersion>,
) -> FileSyncState

Compares a local file (local_sha256) with the server file.

history holds (version, sha256) of every version of the file. Without a stated base, local content equal to an older version counts as outdated, and unknown content as modified (the base is then assumed to be the current version). With a base, local content that differs from both the base and the current version is a conflict once the server moved on.