fluvio docs mismatch with actual behavior

[davidbeesley]

// fluvio/src/offset.rs
    /// Creates a relative offset pointing to the newest log entry
    ///
    /// A relative `FromEnd` offset will point to the last "stable committed"
    /// event entry in the log. Since a log may continue growing at any time,
    /// a `FromEnd` offset may refer to different entries depending on when a
    /// query is made.
    ///
    /// For example, `Offset::end()` will refer to the event with content
    /// `66` at this point in time:
    ///
    /// ```text
    ///         Partition Log: [ .., .., 22, 33, 44, 55, 66 ]
    ///       Absolute Offset:    0,  1,  2,  3,  4,  5,  6
    ///        FromEnd Offset:    6,  5,  4,  3,  2,  1,  0
    /// ```
    ///
    /// But when these new events are added, `Offset::end()` will refer to the
    /// event with content `99`.
    ///
    /// ```text
    ///                                        These events were added!
    ///                                                               |
    ///                                                      vvvvvvvvvv
    ///         Partition Log: [ .., .., 22, 33, 44, 55, 66, 77, 88, 99 ]
    ///       Absolute Offset:    0,  1,  2,  3,  4,  5,  6,  7,  8,  9
    ///        FromEnd Offset:    9,  8,  7,  6,  5,  4,  3,  2,  1,  0
    /// ```
    ///
    /// # Example
    ///
    /// ```
    /// # use fluvio::Offset;
    /// // Creates an offset pointing to the latest log entry
    /// let offset: Offset = Offset::end();
    /// ```
    pub fn end() -> Offset {
        Offset::from_end(0)
    }

    /// Creates a relative offset a fixed distance before the newest log entry
    ///
    /// A relative `FromEnd` offset will begin counting from the last
    /// "stable committed" event entry in the log. Increasing the offset will
    /// select events in reverse chronological order from the most recent event
    /// towards the earliest event. Therefore, a relative `FromEnd` offset may
    /// refer to different entries depending on when a query is made.
    ///
    /// For example, `Offset::from_end(3)` will refer to the event with content
    /// `33` at this point in time:
    ///
    /// ```text
    ///         Partition Log: [ .., .., 22, 33, 44, 55, 66 ]
    ///       Absolute Offset:    0,  1,  2,  3,  4,  5,  6
    ///        FromEnd Offset:    6,  5,  4,  3,  2,  1,  0
    /// ```
    ///
    /// But when these new events are added, `Offset::from_end(3)` will refer to
    /// the event with content `66`:
    ///
    /// ```text
    ///                                        These events were added!
    ///                                                               |
    ///                                                      vvvvvvvvvv
    ///         Partition Log: [ .., .., 22, 33, 44, 55, 66, 77, 88, 99 ]
    ///       Absolute Offset:    0,  1,  2,  3,  4,  5,  6,  7,  8,  9
    ///        FromEnd Offset:    9,  8,  7,  6,  5,  4,  3,  2,  1,  0
    /// ```
    ///
    /// # Example
    ///
    /// ```
    /// # use fluvio::Offset;
    /// // Creates an offset pointing 3 places before the latest log entry
    /// let offset: Offset = Offset::from_end(3);
    /// ```
    pub fn from_end(offset: u32) -> Offset {
        Self {
            inner: OffsetInner::FromEnd(offset as i64),
        }
    }

Actual behavior

    ///                                                      vvvvvvvvvv
    ///         Partition Log: [ .., .., 22, 33, 44, 55, 66, 77, 88, 99 ]
    ///       Absolute Offset:    0,  1,  2,  3,  4,  5,  6,  7,  8,  9
    ///        FromEnd Offset:    10,  0,  8,  7,  6,  5,  4,  3,  2,  1

In other words, calling Offset::end() will get the offset of the next record to be produced.