The --ignore-times comes from the Darcs test suite ~/.darcs/defaults. We 
need to do two things:

1. stick in traces and figure out what darcs is doing
2. reproduce this in test case form

Petr has an explanation about involving lack of cancellation in 
IgnoreTimes DontIgnoreTimes due to not using a mutual exclusivity 
mechanism, but I'm a bit skeptical because it looks like all of Darcs 
code is using the willIgnoreTimes function rather than testing 
[DarcsFlag] directly, which effectively is a mutual exclusivity 
mechanism, albeit a crappy one.  BTW, the real fix is issue1550, ie. 
switching to a command line parsing lib that automagically enforces 
mutual exclusivity

Eric Kow <bugs@darcs.net> writes:
> Petr has an explanation about involving lack of cancellation in
> IgnoreTimes DontIgnoreTimes due to not using a mutual exclusivity
> mechanism, but I'm a bit skeptical because it looks like all of Darcs
> code is using the willIgnoreTimes function rather than testing
> [DarcsFlag] directly, which effectively is a mutual exclusivity
> mechanism, albeit a crappy one.  BTW, the real fix is issue1550, ie.
> switching to a command line parsing lib that automagically enforces
> mutual exclusivity

01:29:01 | morn@twi:~/dev/darcs/mainline -> time darcs wh
No changes!
darcs wh  0,00s user 0,00s system 45% cpu 0,009 total

01:29:03 | morn@twi:~/dev/darcs/mainline -> time darcs wh --ignore
No changes!
darcs wh --ignore  0,17s user 0,03s system 97% cpu 0,206 total

01:29:06 | morn@twi:~/dev/darcs/mainline -> time darcs wh --ignore --no-ignore
No changes!
darcs wh --ignore --no-ignore  0,17s user 0,03s system 97% cpu 0,206 total

01:30:31 | morn@twi:~/dev/darcs/mainline -> time darcs wh --no-ignore --ignore
No changes!
darcs wh --no-ignore --ignore  0,00s user 0,00s system 45% cpu 0,009 total

Draw whatsoever conclusions you want from this...

Yours,
   Petr.

This has been fixed somewhere between 2.14 and 2.16 as part of the 
effort to make read-only repositories work, at least if the index is 
ignored i.e. --ignore-times is in effect. See patch

patch 248f84c2847cc7c453c395be6b73c3cb0ada8d92
Author: Ben Franksen <ben.franksen@online.de>
Date:   Mon Dec  3 19:33:14 CET 2018
  * resolve issue1959: read-only commands should not need write 
access to the index