New timezone option: seconds since unix epoch

[murgeljm]

• Closes Unix epoch timestamp display option; copy-able field #4866

What

Added a unix epoch timestamp display option, as mentioned in issue 4866

Not quite sure how compact time display should be handled:

    /// Useful when showing dates/times on a timeline
    /// and you want it compact.
    ///
    /// Shows dates when zoomed out, shows times when zoomed in,
    /// shows relative millisecond when really zoomed in.
    pub fn format_time_compact(&self, time_zone_for_timestamps: TimeZone) -> String {
...
            if let Some(datetime) = self.to_datetime() {
                let is_whole_minute = ns % 60_000_000_000 == 0;
                let time_format = if self.is_exactly_midnight() {
                    "[year]-[month]-[day]"
                } else if is_whole_minute {
                    "[hour]:[minute]"
                } else {
-                    "[hour]:[minute]:[second]"
+                    Self::get_time_prefix(&time_zone_for_timestamps)
                };
                let parsed_format = time::format_description::parse(time_format).unwrap();

                return Self::time_string(datetime, &parsed_format, time_zone_for_timestamps);
            }
...
}

Should the [hour]:[minute] be changed as well when unix timestamp is chosen?

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[emilk]

format_time_compact could, for instance, show the number of seconds since epoch if we're on a whole second, else show the offset since the last second.

[murgeljm]

format_time_compact could, for instance, show the number of seconds since epoch if we're on a whole second, else show the offset since the last second.

yup, that is already implemented, basically for unix epoch display everywhere there was a whole second in the format i show unix epoch instead - but if there is a time display with no seconds shown (on a whole minute) I don't know which would be better:
[ ] show unix epoch instead of hours:minute (could look busy for a compact display?)
[ ] show hours:minute regardless of the unix epoch setting (disregarding user preference)

Also another question, should I label pull request myself with include/exclude in changelog? Or is that something maintainers do?

[emilk]

I think that if the user has selected the option for "seconds since unix epoch", we should always use seconds, everywhere - no minutes or hours.

As for labels: only maintainers can add labels. I haven't found any GitHub option to allow contributors to add labels.

[emilk]

Works great - thanks for the PR!