[tz] Estimate for a new tzdb release with Brazil rules.

[Paul Eggert]

On 5/14/19 2:49 AM, Stephen Colebourne wrote:
> FYI, the Java definition says this when querying the list of available
> versions:
> https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/time/zone/ZoneRulesProvider.html#getVersions(java.lang.String)
>
>      * The exact meaning and format of the version is provider specific.
>      * The version must follow lexicographical order, thus the returned map will
>      * be order from the oldest known rules to the newest available rules.
>      * The default 'TZDB' group uses version numbering consisting of the year
>      * followed by a letter, such as '2009e' or '2012f'.

The current tzdb release numbering scheme allows for more than 26
releases per year. tz-link.html says:

Since 1996, each version has been a four-digit year followed by
lower-case letter (<samp>a</samp> through <samp>z</samp>,
then <samp>za</samp> through <samp>zz</samp>, then <samp>zza</samp>
through <samp>zzz</samp>, and so on).

As that sentence suggests, we may change the release numbering scheme in
the future (we've changed it in the past). That would not be a casual
decision of course.

> The ordering allows the versions to be sorted, and the latest one
> selected. If users want to have their own versions, I'd strongly
> suggest something sortable, not something based off a git hash, such
> as 2019a-patched-2019-05-14.

The default numbering scheme for non-release versions is sortable,
although one should use something like GNU strverscmp rather than
classic strcmp. For example, "2019a-14-g9e498e2" is the version number
for 14 commits since 2019a.

The Java documentation should probably be updated to reflect the above.
At least it should mention the possibility of "2019za" (shudder).