doc/rev-list-options: explain "-g" output formats

We document that asking for HEAD@{now} will switch the output to show HEAD@{timestamp}, but not that specifying `--date` has a similar effect, or that it can be overridden with HEAD@{0}. Let's do so. These rules come from 794151e (reflog-walk: always make HEAD@{0} show indexed selectors, 2012-05-04), though that is simply the culmination of years of these heuristics growing organically. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed Jul 22, 2016 at 15:51 UTC 83c9f95cce99bcd383c78d614d614e72a4015e59
1 file changed +19 -4
Documentation/rev-list-options.txt
+19 -4
@@ -252,10 +252,25 @@ list.
252 +
253 With `--pretty` format other than `oneline` (for obvious reasons),
254 this causes the output to have two extra lines of information
255 -taken from the reflog. By default, `ref@{Nth}` notation is
256 -used in the output. When the starting commit is specified as
257 -`ref@{now}`, output also uses `ref@{timestamp}` notation
258 -instead. Under `--pretty=oneline`, the commit message is
255 +taken from the reflog. The reflog designator in the output may be shown
256 +as `ref@{Nth}` (where `Nth` is the reverse-chronological index in the
257 +reflog) or as `ref@{timestamp}` (with the timestamp for that entry),
258 +depending on a few rules:
259 ++
260 +--
261 +1. If the starting point is specified as `ref@{Nth}`, show the index
262 +format.
263 ++
264 +2. If the starting point was specified as `ref@{now}`, show the
265 +timestamp format.
266 ++
267 +3. If neither was used, but `--date` was given on the command line, show
268 +the timestamp in the format requested by `--date`.
269 ++
270 +4. Otherwise, show the index format.
271 +--
272 ++
273 +Under `--pretty=oneline`, the commit message is
274 prefixed with this information on the same line.
275 This option cannot be combined with `--reverse`.
276 See also linkgit:git-reflog[1].