Hi!

Original snippet:
-- >8 --
.Dd
.Dt DU 1
.Os
.Sh NAME
.Nm du
.Nd disk usage
.Sh OPTIONS
.Bl -tag -compact
.It Fl -time-style Ns = Ns Cm iso
Equivalent to
.ds qq \&"
.Fl -time-style Ns = Ns Cm + Ns Li "\*(qq%F\*(qq\ \ \ \ \ \ \ \ \ "
.Ar ( YYYY Ns Cm - Ns Ar MM Ns Cm - Ns Ar DD
\(em the
.St -iso8601
date format).
.It Fl -time-style Ns = Ns Cm long-iso
Equivalent to
.Fl -time-style Ns = Ns Cm + Ns Li "\*(qq%F\ %R\*(qq\ \ \ \ \ \ "
.Pq Ar YYYY Ns Cm - Ns Ar MM Ns Cm - Ns Ar DD HH Ns Cm \&: Ns Ar MM .
.It Fl -time-style Ns = Ns Cm full-iso
Equivalent to
.Fl -time-style Ns = Ns Cm + Ns Li "\*(qq%F\ %T.%N\ %z\*(qq"
.Pq Ar YYYY Ns Cm - Ns Ar MM Ns Cm - Ns Ar DD HH Ns Cm \&: Ns Ar MM Ns Cm \&: Ns Ar MM Ns Cm \&. Ns Ar NSNSNSNSN Cm \(+- Ns Ar TZTZ .
.It Fl -time-style Ns = Ns Cm + Ns Ar date-format
.El
-- >8 --

groff renders this, as expected, as 
-- >8 --
     --time-style=iso
             Equivalent to --time-style=+"%F"          (YYYY-MM-DD — the ISO 8601 date format).
     --time-style=long-iso
             Equivalent to --time-style=+"%F %R"       (YYYY-MM-DD HH:MM).
     --time-style=full-iso
             Equivalent to --time-style=+"%F %T.%N %z" (YYYY-MM-DD HH:MM:MM.NSNSNSNSN ±TZTZ).
     --time-style=+date-format
-- >8 --

mandoc trunk (as of fifteen minutes ago) renders this as
-- >8 --
     ----ttiimmee--ssttyyllee=iissoo
             Equivalent to ----ttiimmee--ssttyyllee=++ %F"         " (_Y_Y_Y_Y--_M_M--_D_D — the ISO
             8601 date format).
     ----ttiimmee--ssttyyllee=lloonngg--iissoo
             Equivalent to ----ttiimmee--ssttyyllee=++ %F %R"      " (_Y_Y_Y_Y--_M_M--_D_D _H_H::_M_M).
     ----ttiimmee--ssttyyllee=ffuullll--iissoo
             Equivalent to ----ttiimmee--ssttyyllee=++ %F %T.%N %z"" (_Y_Y_Y_Y--_M_M--_D_D
             _H_H::_M_M::_M_M.._N_S_N_S_N_S_N_S_N ±±_T_Z_T_Z).
     ----ttiimmee--ssttyyllee=++_d_a_t_e_-_f_o_r_m_a_t
-- >8 --


Simplified:
-- >8 --
.ds qq \&"
.Sy "\*(qq a \*(qq b"
-- >8 --

groff renders this as:
-- >8 --
     " a " b
-- >8 --
(single argument containing " a " b)

but mandoc trunk as:
-- >8 --
      aa "" bb""
-- >8 --


Inlining the string as
-- >8 --
.Sy "\&" a \&" b"
-- >8 --
(three arguments, one with just \&, the second a, the third " b")
makes groff output the same thing as mandoc.


This is non-critical for me, since I was just trying to come up with a
less annoying spelling for this, but it's nevertheless a groff
incompatibility.

Best,
наб