test, provide regression tests for ddiff'ing timezone'd stamps

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
fix, PEBKAC, also use the tz from --from-zone for ddiff's stdin

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
fix, PEBKAC, check if zone is fixed-up already in dt_io_strpdt_ep() and friends

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
minor, rework try_zone() allowing the colon-separator to be optional

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
fix, also consider zone specs +00:00, set the znfxd flag

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
hygiene, don't advance pointers that need to be decremented on non-local exits to work properly

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
minor, also keep track of zone specs given via the %Z flag

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
fix, PEBKAC, reassign end pointer after try_zone() back to traversal pointer sp

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
Merge branch 'tool/ddiff' into next

* tool/ddiff:
  fix, PEBKAC, reassign end pointer after try_zone() back to traversal pointer sp
  minor, also keep track of zone specs given via the %Z flag
  hygiene, don't advance pointers that need to be decremented on non-local exits to work properly
  fix, also consider zone specs +00:00, set the znfxd flag
  minor, rework try_zone() allowing the colon-separator to be optional
  fix, PEBKAC, check if zone is fixed-up already in dt_io_strpdt_ep() and friends
  fix, PEBKAC, also use the tz from --from-zone for ddiff's stdin
  test, provide regression tests for ddiff'ing timezone'd stamps