v0.5.0

Layouts from a format string. Every input parses to what it did in 0.4.2.

Added

• Layout.fromFormatString(dialect, format, opts), the inverse of
  formatString: a layout from a strftime, Go or Java format string, for a
  column whose format is known, so that no value is detected. The order is
  the format's, so %d/%m/%Y gives a reusable layout where one detected
  from 13/02/2024 is decided per value. Each dialect reads as its own
  parser does, within what a layout holds: a one-or-two-digit field takes
  either, %f one to nine digits, %z Z or either offset form, and a
  month or weekday name any month or weekday in English and the options'
  locales. error.Unsupported for a field no layout reads,
  error.InvalidFormat for a string that is no date format, and
  error.NoBaseTime for one with no year and no base time. Through C as
  dateparsa_layout_from_format and through Python as
  Layout.from_format. Two fuzz targets hold it: a layout's format string
  read back reads the value it was spelled from to the same time, and
  agrees with the layout wherever both read; and a layout from any format
  string spells formats that read back to the same time. (#27)

Changed

• A reused layout whose fields all have fixed widths (ISO 8601, RFC 3339,
  SQL, compact dates) reads a value in about 0.9 of the time it did: an ISO
  date-time in 9.7 ns where it took 10.3, an ISO date in 6.8 where it took
  7.8, on an M5 Max. The fixed-slot path is inlined into execute by hand.
• formatString spells from any value the layout reads, not only the one
  it was detected from at the same widths: a layout from 1/2/2024 spells
  11/12/2024 as %m/%d/%Y where it gave error.NotDetectedFrom. Python's
  Layout.format_string takes the value as value=.
• formatString writes text between two fields as one run, so Java quotes
  it once; refuses a NUL, which no C format string holds; spells a literal
  T after a one-or-two-digit day rather than refusing it; spells a
  weekday only in English and the locales the layout reads, and only as a
  whole word, as a format string reads one; and refuses any format
  fromFormatString would not read back, such as one with more runs of
  text than a layout has fields.