urbit/pkg/arvo/lib/hood/kiln.hoon

::                                                      ::  ::
::::  /hoon/kiln/hood/lib                               ::  ::
  ::                                                    ::  ::
/?  310                                                 ::  version
::                                                      ::  ::
::::                                                    ::  ::
  ::                                                    ::  ::
=,  clay
=,  space:userlib
=,  format
|%                                                      ::  ::
++  part  {$kiln $0 pith}                               ::  kiln state
++  pith                                                ::  ::
    $:  rem=(map desk per-desk)                         ::
        syn=(map kiln-sync let/@ud)                     ::
        ota=(unit [=ship =desk =aeon])                  ::
        commit-timer=[way=wire nex=@da tim=@dr mon=term]
    ==                                                  ::
++  per-desk                                            ::  per-desk state
    $:  auto/?                                          ::  escalate on failure
        gem/germ                                        ::  strategy
        her/@p                                          ::  from ship
        sud/@tas                                        ::  from desk
        cas/case                                        ::  at case
    ==                                                  ::
::                                                      ::  ::
::::                                                    ::  ::
  ::                                                    ::  ::
++  kiln-commit  term                                   ::
++  kiln-mount                                          ::
    $:  pax/path                                        ::
        pot/term                                        ::
    ==                                                  ::
++  kiln-unmount  $@(term {knot path})                  ::
++  kiln-sync                                           ::
    $:  syd/desk                                        ::
        her/ship                                        ::
        sud/desk                                        ::
    ==                                                  ::
++  kiln-unsync                                         ::
    $:  syd/desk                                        ::
        her/ship                                        ::
        sud/desk                                        ::
    ==                                                  ::
++  kiln-merge                                          ::
    $:  syd/desk                                        ::
        ali/ship                                        ::
        sud/desk                                        ::
        cas/case                                        ::
        gim/?($auto germ)                               ::
    ==                                                  ::
--                                                      ::
::                                                      ::  ::
::::                                                    ::  ::
  ::                                                    ::  ::
|=  {bowl:gall part}                                    ::  main kiln work
?>  =(src our)
|_  moz/(list card:agent:gall)
++  abet                                                ::  resolve
  [(flop moz) `part`+<+.$]
::
++  emit
  |=  card:agent:gall
  %_(+> moz [+< moz])
::
++  emil                                              ::  return cards
  |=  (list card:agent:gall)
  ^+  +>
  ?~(+< +> $(+< t.+<, +> (emit i.+<)))
::
++  render
  |=  {mez/tape sud/desk who/ship syd/desk}
  :^  %palm  [" " ~ ~ ~]  leaf+(weld "kiln: " mez)
  ~[leaf+"from {<sud>}" leaf+"on {<who>}" leaf+"to {<syd>}"]
::
++  poke-commit
  |=  [mon/kiln-commit auto=?]
  =<  abet
  =.  +>.$  (emit %pass /commit %arvo %c [%dirk mon])
  ?.  auto
    +>.$
  =/  recur  ~s1
  =.  commit-timer
    [/kiln/autocommit (add now recur) recur mon]
    (emit %pass way.commit-timer %arvo %b [%wait nex.commit-timer])
::
++  poke-autocommit
  |=  [mon/kiln-commit auto=?]
  =<  abet
  =.  +>.$  (emit %pass /commit %arvo %c [%dirk mon])
  ?.  auto
    +>.$
  =/  recur  ~s1
  =.  commit-timer
    [/kiln/autocommit (add now recur) recur mon]
  (emit %pass way.commit-timer %arvo %b [%wait nex.commit-timer])
::
++  poke-cancel-autocommit
  |=  ~
  abet:(emit %pass way.commit-timer %arvo %b [%rest nex.commit-timer])
::
++  poke-mount
  |=  kiln-mount
  =+  bem=(de-beam pax)
  ?~  bem
    =+  "can't mount bad path: {<pax>}"
    abet:(spam leaf+- ~)
  abet:(emit %pass /mount %arvo %c [%mont pot u.bem])
::
++  poke-unmount
  |=  mon/kiln-unmount
  ?^  mon
    =+  bem=(de-beam mon)
    ?~  bem
      =+  "can't unmount bad path: {<mon>}"
      abet:(spam leaf+- ~)
    abet:(emit %pass /unmount-beam %arvo %c [%ogre [[p q r] s]:u.bem])
  abet:(emit %pass /unmount-point %arvo %c [%ogre mon])
::
++  poke-track                                        ::
  |=  hos/kiln-sync
  ?:  (~(has by syn) hos)
    abet:(spam (render "already tracking" [sud her syd]:hos) ~)
  abet:abet:start-track:(auto hos)
::
++  update
  |%
  ++  make-wire
    |=  =path
    ?>  ?=(^ ota)
    %-  welp
    :_  path
    /kiln/ota/(scot %p ship.u.ota)/[desk.u.ota]/(scot %ud aeon.u.ota)
  ::
  ++  check-ota
    |=  =wire
    ?~  ota
      |
    ~!  ota=ota
    ?&  ?=([@ @ @ *] wire)
        =(i.wire (scot %p ship.u.ota))
        =(i.t.wire desk.u.ota)
        =(i.t.t.wire (scot %ud aeon.u.ota))
    ==
  ::
  ++  render
    |=  [mez=tape error=(unit (pair term tang))]
    %+  spam
      ?~  ota
        leaf+mez
      :^  %palm  [" " ~ ~ ~]  leaf+(weld "kiln: " mez)
      ~[leaf+"from {<desk.u.ota>}" leaf+"on {<ship.u.ota>}"]
    ?~  error
      ~
    [>p.u.error< q.u.error]
  ::
  ++  render-ket
    |=  [mez=tape error=(unit (pair term tang))]
    ?>  ?=(^ ota)
    =<  ?>(?=(^ ota) .)
    %+  spam
      :^  %palm  [" " ~ ~ ~]  leaf+(weld "kiln: " mez)
      ~[leaf+"from {<desk.u.ota>}" leaf+"on {<ship.u.ota>}"]
    ?~  error
      ~
    [>p.u.error< q.u.error]
  ::
  ++  poke
    |=  arg=(unit [=ship =desk])
    abet:(poke-internal arg)
  ::
  ++  poke-internal
    |=  arg=(unit [=ship =desk])
    ^+  ..abet
    =?  ..abet  =(arg (bind ota |=([=ship =desk =aeon] [ship desk])))
      (render "restarting OTA sync" ~)
    =?  ..abet  ?=(^ ota)
      =.  ..abet  (render-ket "cancelling OTA sync" ~)
      ..abet(ota ~)
    ?~  arg
      ..abet
    =.  ota  `[ship.u.arg desk.u.arg *aeon]
    =.  ..abet  (render "starting OTA sync" ~)
    %:  emit
      %pass  (make-wire /find)  %arvo  %c
      %warp  ship.u.arg  desk.u.arg  `[%sing %y ud+1 /]
    ==
  ::
  ++  take
    |=  [=wire =sign-arvo]
    ^+  ..abet
    ?>  ?=(^ ota)
    ?.  (check-ota wire)
      ..abet
    ?.  ?=([@ @ @ @ *] wire)
      ..abet
    ?+  i.t.t.t.wire  ~&([%strange-ota-take t.t.t.wire] ..abet)
      %find        (take-find sign-arvo)
      %sync        (take-sync sign-arvo)
      %merge-home  (take-merge-home sign-arvo)
      %merge-kids  (take-merge-kids sign-arvo)
    ==
  ::
  ++  take-find
    |=  =sign-arvo
    ?>  ?=(%writ +<.sign-arvo)
    ?>  ?=(^ ota)
    =.  ..abet  (render-ket "activated OTA" ~)
    %:  emit
      %pass  (make-wire /sync)  %arvo  %c
      %warp  ship.u.ota  desk.u.ota  `[%sing %w da+now /]
    ==
  ::
  ++  take-sync
    |=  =sign-arvo
    ^+  ..abet
    ?>  ?=(%writ +<.sign-arvo)
    ?>  ?=(^ ota)
    ?~  p.sign-arvo
      =.  ..abet  (render-ket "OTA cancelled, retrying" ~)
      (poke-internal `[ship desk]:u.ota)
    =?  aeon.u.ota  ?=($w p.p.u.p.sign-arvo)
      ud:;;(cass:clay q.q.r.u.p.sign-arvo)
    =/  =germ
      =+  .^(=cass:clay %cw /(scot %p our)/home/(scot %da now))
      ?:  =(0 ud.cass)
        %init
      ?:((gth 2 ud.cass) %that %mate)
    =.  ..abet  (render-ket "beginning OTA to %home" ~)
    %:  emit
      %pass  (make-wire /merge-home)  %arvo  %c
      %merg  %home  ship.u.ota  desk.u.ota  ud+aeon.u.ota  germ
    ==
  ::
  ++  take-merge-home
    |=  =sign-arvo
    ?>  ?=(%mere +<.sign-arvo)
    ?>  ?=(^ ota)
    ?:  ?=([%| %ali-unavailable *] p.sign-arvo)
      =.  ..abet
        =/  =tape  "OTA to %home failed, maybe because sunk; restarting"
        (render-ket tape `p.p.sign-arvo)
      (poke-internal `[ship desk]:u.ota)
    ::
    ?:  ?=(%| -.p.sign-arvo)
      =.  ..abet
        =/  =tape  "OTA to %home failed, waiting for next revision"
        (render-ket tape `p.p.sign-arvo)
      =.  aeon.u.ota  +(aeon.u.ota)
      %:  emit
        %pass  (make-wire /sync)  %arvo  %c
        %warp  ship.u.ota  desk.u.ota  `[%sing %y ud+aeon.u.ota /]
      ==
    =.  ..abet  (render-ket "OTA to %home succeeded" ~)
    =.  ..abet  (render-ket "beginning OTA to %kids" ~)
    =/  =germ
      =+  .^(=cass:clay %cw /(scot %p our)/kids/(scot %da now))
      ?:  =(0 ud.cass)
        %init
      ?:((gth 2 ud.cass) %that %mate)
    %:  emit
      %pass  (make-wire /merge-kids)  %arvo  %c
      %merg  %kids  ship.u.ota  desk.u.ota  ud+aeon.u.ota  germ
    ==
  ::
  ++  take-merge-kids
    |=  =sign-arvo
    ?>  ?=(%mere +<.sign-arvo)
    ?>  ?=(^ ota)
    ?:  ?=([%| %ali-unavailable *] p.sign-arvo)
      =.  ..abet
        =/  =tape  "OTA to %kids failed, maybe because sunk; restarting"
        (render-ket tape `p.p.sign-arvo)
      (poke-internal `[ship desk]:u.ota)
    ::
    =.  ..abet
      ?-  -.p.sign-arvo
        %&  (render-ket "OTA to %kids succeeded" ~)
        %|  (render-ket "OTA to %kids failed" `p.p.sign-arvo)
      ==
    =.  aeon.u.ota  +(aeon.u.ota)
    %:  emit
      %pass  (make-wire /sync)  %arvo  %c
      %warp  ship.u.ota  desk.u.ota  `[%sing %y ud+aeon.u.ota /]
    ==
  --
::
++  poke-sync                                         ::
  |=  hos/kiln-sync
  ?:  (~(has by syn) hos)
    abet:(spam (render "already syncing" [sud her syd]:hos) ~)
  abet:abet:start-sync:(auto hos)
::
++  poke-syncs                                        ::  print sync config
  |=  ~
  =<  abet  %-  spam
  :-  [%leaf "OTAs from {<ota>}"]
  ?:  =(0 ~(wyt by syn))
    [%leaf "no syncs configured"]~
  %+  turn  ~(tap in ~(key by syn))
  |=(a/kiln-sync (render "sync configured" [sud her syd]:a))
::
++  poke-unsync                                         ::
  |=  hus/kiln-unsync
  ?.  (~(has by syn) hus)
    abet:(spam (render "not syncing" [sud her syd]:hus) ~)
  %*  .  abet:abet:stop:(auto hus)
    syn  (~(del by syn) hus)
  ==
::
++  poke-merge                                        ::
  |=  kiln-merge
  abet:abet:(merge:(work syd) ali sud cas gim)
::
++  poke-cancel
  |=  ~
  abet:(emit %pass /cancel %arvo %c [%drop %foo])
::
++  poke-info
  |=  {mez/tape tor/(unit toro)}
  ?~  tor
    abet:(spam leaf+mez ~)
  abet:(emit:(spam leaf+mez ~) %pass /kiln %arvo %c [%info u.tor])
::
++  poke-rm
  |=  a/path
  =+  b=.^(arch %cy a)
  ?~  fil.b
    =+  ~[leaf+"No such file:" leaf+"{<a>}"]
    abet:(spam -)
  (poke-info "removed" `(fray a))
::
++  poke-label
  |=  {syd/desk lab/@tas}
  =+  pax=/(scot %p our)/[syd]/[lab]
  (poke-info "labeled {(spud pax)}" `[syd %| lab])
::
++  poke-schedule
  |=  {where/path tym/@da eve/@t}
  =.  where  (welp where /sched)
  %+  poke-info  "scheduled"
  =+  old=;;((map @da cord) (fall (file where) ~))
  `(foal where %sched !>((~(put by old) tym eve)))
::
++  poke-permission
  |=  {syd/desk pax/path pub/?}
  =<  abet
  %-  emit
  =/  =rite  [%r ~ ?:(pub %black %white) ~]
  [%pass /kiln/permission %arvo %c [%perm syd pax rite]]
::
++  poke
  |=  [=mark =vase]
  ?+  mark  ~|([%poke-kiln-bad-mark mark] !!)
    %kiln-commit             =;(f (f !<(_+<.f vase)) poke-commit)
    %kiln-autocommit         =;(f (f !<(_+<.f vase)) poke-autocommit)
    %kiln-info               =;(f (f !<(_+<.f vase)) poke-info)
    %kiln-label              =;(f (f !<(_+<.f vase)) poke-label)
    %kiln-cancel             =;(f (f !<(_+<.f vase)) poke-cancel)
    %kiln-mount              =;(f (f !<(_+<.f vase)) poke-mount)
    %kiln-rm                 =;(f (f !<(_+<.f vase)) poke-rm)
    %kiln-schedule           =;(f (f !<(_+<.f vase)) poke-schedule)
    %kiln-track              =;(f (f !<(_+<.f vase)) poke-track)
    %kiln-sync               =;(f (f !<(_+<.f vase)) poke-sync)
    %kiln-ota                =;(f (f !<(_+<.f vase)) poke:update)
    %kiln-syncs              =;(f (f !<(_+<.f vase)) poke-syncs)
    %kiln-goad-gall          =;(f (f !<(_+<.f vase)) poke-goad-gall)
    %kiln-unmount            =;(f (f !<(_+<.f vase)) poke-unmount)
    %kiln-unsync             =;(f (f !<(_+<.f vase)) poke-unsync)
    %kiln-permission         =;(f (f !<(_+<.f vase)) poke-permission)
    %kiln-cancel-autocommit  =;(f (f !<(_+<.f vase)) poke-cancel-autocommit)
    %kiln-merge              =;(f (f !<(_+<.f vase)) poke-merge)
  ==
::
++  poke-goad-gall
  |=  [force=? agent=(unit dude:gall)]
  abet:(emit %pass /kiln %arvo %g %goad force agent)
::
++  done
  |=  {way/wire saw/(unit error:ames)}
  ~?  ?=(^ saw)  [%kiln-nack u.saw]
  abet
::
++  take-agent
  |=  [=wire =sign:agent:gall]
  ?+  wire  ~|([%kiln-bad-take-agent wire -.sign] !!)
    [%kiln %fancy *]   ?>  ?=(%poke-ack -.sign)
                       (take-coup-fancy t.t.wire p.sign)
    [%kiln %spam *]    ?>  ?=(%poke-ack -.sign)
                       (take-coup-spam t.t.wire p.sign)
  ==
::
++  take-general
  |=  [=wire =sign-arvo]
  ?-  wire
      [%sync %merg *]   %+  take-mere-sync  t.t.wire
                        ?>(?=(%mere +<.sign-arvo) +>.sign-arvo)
      [%find-ship *]    %+  take-writ-find-ship  t.wire
                        ?>(?=(%writ +<.sign-arvo) +>.sign-arvo)
      [%sync *]         %+  take-writ-sync  t.wire
                        ?>(?=(%writ +<.sign-arvo) +>.sign-arvo)
      [%autocommit *]   %+  take-wake-autocommit  t.wire
                        ?>(?=(%wake +<.sign-arvo) +>.sign-arvo)
      [%ota *]          abet:(take:update t.wire sign-arvo)
      *
    ?+  +<.sign-arvo  ~|([%kiln-bad-take-card +<.sign-arvo] !!)
      %done  %+  done  wire
             ?>(?=(%done +<.sign-arvo) +>.sign-arvo)
      %mere  %+  take-mere  wire
             ?>(?=(%mere +<.sign-arvo) +>.sign-arvo)
    ==
  ==
++  take  |=(way/wire ?>(?=({@ ~} way) (work i.way))) ::  general handler
++  take-mere                                         ::
  |=  {way/wire are/(each (set path) (pair term tang))}
  abet:abet:(mere:(take way) are)
::
++  take-coup-fancy                                   ::
  |=  {way/wire saw/(unit tang)}
  abet:abet:(coup-fancy:(take way) saw)
::
++  take-coup-spam                                    ::
  |=  {way/wire saw/(unit tang)}
  ~?  ?=(^ saw)  [%kiln-spam-lame u.saw]
  abet
::
++  take-mere-sync                                    ::
  |=  {way/wire mes/(each (set path) (pair term tang))}
  ?>  ?=({@ @ @ *} way)
  =/  hos/kiln-sync
      :*  syd=(slav %tas i.way)
          her=(slav %p i.t.way)
          sud=(slav %tas i.t.t.way)
      ==
  abet:abet:(mere:(auto hos) mes)
::
++  take-writ-find-ship                               ::
  |=  {way/wire rot/riot}
  ?>  ?=({@ @ @ *} way)
  =/  hos/kiln-sync
      :*  syd=(slav %tas i.way)
          her=(slav %p i.t.way)
          sud=(slav %tas i.t.t.way)
      ==
  abet:abet:(take-find-ship:(auto hos) rot)
::
++  take-writ-sync                                    ::
  |=  {way/wire rot/riot}
  ?>  ?=({@ @ @ *} way)
  =/  hos/kiln-sync
      :*  syd=(slav %tas i.way)
          her=(slav %p i.t.way)
          sud=(slav %tas i.t.t.way)
      ==
  abet:abet:(writ:(auto hos) rot)
::
++  take-wake-autocommit
  |=  [way=wire error=(unit tang)]
  ?^  error
    %-  (slog u.error)
    ~&  %kiln-wake-autocommit-fail
    abet
  =.  nex.commit-timer  (add now tim.commit-timer)
  =<  abet
  %-  emil
  :~  [%pass /commit %arvo %c [%dirk mon.commit-timer]]
      [%pass way.commit-timer %arvo %b [%wait nex.commit-timer]]
  ==
::
::
++  spam
  |=  mes/(list tank)
  ((slog mes) ..spam)
::
++  auto
  |=  kiln-sync
  =+  (~(gut by syn) [syd her sud] let=*@ud)
  |%
  ++  abet
    ..auto(syn (~(put by syn) [syd her sud] let))
  ::
  ++  blab
    |=  new/(list card:agent:gall)
    ^+  +>
    +>.$(moz (welp new moz))
  ::
  ++  warp
    |=  [=wire =ship =riff]
    (blab [%pass wire %arvo %c [%warp ship riff]] ~)
  ::
  ++  spam  |*(* %_(+> ..auto (^spam +<)))
  ++  stop
    =>  (spam (render "ended autosync" sud her syd) ~)
    =/  =wire  /kiln/sync/[syd]/(scot %p her)/[sud]
    (warp wire her sud ~)
  ::  XX duplicate of start-sync? see |track
  ::
  ++  start-track
    =>  (spam (render "activated track" sud her syd) ~)
    =.  let  1
    =/  =wire  /kiln/sync/[syd]/(scot %p her)/[sud]
    (warp wire her sud `[%sing %y ud+let /])
  ::
  ++  start-sync
    =>  (spam (render "finding ship and desk" sud her syd) ~)
    =/  =wire  /kiln/find-ship/[syd]/(scot %p her)/[sud]
    (warp wire her sud `[%sing %y ud+1 /])
  ::
  ++  take-find-ship
    |=  rot=riot
    =>  (spam (render "activated sync" sud her syd) ~)
    =/  =wire  /kiln/sync/[syd]/(scot %p her)/[sud]
    (warp wire her sud `[%sing %w [%da now] /])
  ::
  ++  writ
    |=  rot=riot
    ?~  rot
      =.  +>.$
        %^    spam
            leaf+"sync cancelled, retrying"
          (render "on sync" sud her syd)
        ~
      start-sync
    =.  let  ?.  ?=($w p.p.u.rot)  let  ud:;;(cass:clay q.q.r.u.rot)
    =/  =wire  /kiln/sync/merg/[syd]/(scot %p her)/[sud]
    ::  germ: merge mode for sync merges
    ::
    ::    Initial merges from any source must use the %init germ.
    ::    Subsequent merges may use any germ, but if the source is
    ::    a remote ship with which we have not yet merged, we won't
    ::    share a merge-base commit and all germs but %that will fail.
    ::
    ::    We want to always use %that for the first remote merge.
    ::    But we also want local syncs (%base to %home or %kids)
    ::    to succeed after that first remote sync. To accomplish both
    ::    we simply use %that for the first three sync merges.
    ::    (The first two are from the pill.)
    ::
    =/  =germ
      =/  =cass
        .^(cass:clay %cw /(scot %p our)/[syd]/(scot %da now))
      ?:  =(0 ud.cass)
        %init
      ?:((gth 2 ud.cass) %that %mate)
    =<  %-  spam
        ?:  =(our her)  ~
        [(render "beginning sync" sud her syd) ~]
    (blab [%pass wire %arvo %c [%merg syd her sud ud+let germ]] ~)
  ::
  ++  mere
    |=  mes=(each (set path) (pair term tang))
    ?:  ?=([%| %ali-unavailable *] mes)
      =.  +>.$
        %^    spam
            leaf+"merge cancelled, maybe because sunk; restarting"
          (render "on sync" sud her syd)
        ~
      start-sync:stop
    =.  let  +(let)
    =.  +>.$
      %-  spam
      ?:  ?=(%& -.mes)
        [(render "sync succeeded" sud her syd) ~]
      ?+  p.p.mes
        :*  (render "sync failed" sud her syd)
            leaf+"please manually merge the desks with"
            leaf+"|merge %{(trip syd)} {(scow %p her)} %{(trip sud)}"
            leaf+""
            leaf+"error code: {<p.p.mes>}"
            q.p.mes
        ==
      ::
          $no-ali-disc
        :~  (render "sync activated" sud her syd)
            leaf+"note: blank desk {<sud>} on {<her>}"
        ==
      ==
    =/  =wire  /kiln/sync/[syd]/(scot %p her)/[sud]
    (warp wire her sud `[%sing %y ud+let /])
  --
::
++  work                                              ::  state machine
  |=  syd/desk
  =/  ,per-desk
      %+  ~(gut by rem)  syd
      =+  *per-desk
      %_(- cas [%da now])
  |%
  ++  abet                                            ::  resolve
    ..work(rem (~(put by rem) syd auto gem her sud cas))
  ::
  ++  blab
    |=  new/(list card:agent:gall)
    ^+  +>
    +>.$(moz (welp new moz))
  ::
  ++  win   .                                         ::  successful poke
  ++  lose
    ^+  .
    ~|  %kiln-work-fail
    .
  ::
  ++  perform                                         ::
    ^+  .
    (blab [%pass /kiln/[syd] %arvo %c [%merg syd her sud cas gem]] ~)
  ::
  ++  fancy-merge                                     ::  send to self
    |=  {syd/desk her/@p sud/desk gem/?($auto germ)}
    ^+  +>
    =/  =cage  [%kiln-merge !>([syd her sud cas gem])]
    %-  blab  :_  ~
    [%pass /kiln/fancy/[^syd] %agent [our %hood] %poke cage]
  ::
  ++  spam  ::|=(tang ((slog +<) ..spam))
            |*(* +>(..work (^spam +<)))
  ++  merge
    |=  {her/@p sud/@tas cas/case gim/?($auto germ)}
    ^+  +>
    ?.  ?=($auto gim)
      perform(auto |, gem gim, her her, cas cas, sud sud)
    ?:  =(0 ud:.^(cass:clay %cw /(scot %p our)/[syd]/(scot %da now)))
      =>  $(gim %init)
      .(auto &)
    =>  $(gim %fine)
    .(auto &)
  ::
  ++  coup-fancy
    |=  saw/(unit tang)
    ?~  saw
      +>
    =+  :-  "failed to set up conflict resolution scratch space"
        "I'm out of ideas"
    lose:(spam leaf+-< leaf+-> u.saw)
  ::
  ++  mere
    |=  are/(each (set path) (pair term tang))
    ^+  +>
    ?:  =(%meld gem)
      ?:  ?=(%& -.are)
        ?.  auto
          =+  "merged with strategy {<gem>}"
          win:(spam leaf+- ?~(p.are ~ [>`(set path)`p.are< ~]))
        :: ~?  >  =(~ p.are)  [%mere-no-conflict syd]
        =>  .(+>.$ (spam leaf+"mashing conflicts" ~))
        =+  tic=(cat 3 syd '-scratch')
        =/  notations=(list [path (unit [mark vase])])
          %+  turn  ~(tap in p.are)
          |=  =path
          =/  =mark    -:(flop path)
          =/  =dais    .^(dais %cb /(scot %p our)/[syd]/(scot cas)/[mark])
          =/  base     .^(vase %cr (weld /(scot %p our)/[tic]/(scot cas) path))
          =/  ali      .^(vase %cr (weld /(scot %p her)/[sud]/(scot cas) path))
          =/  bob      .^(vase %cr (weld /(scot %p our)/[syd]/(scot cas) path))
          =/  ali-dif  (~(diff dais base) ali)
          =/  bob-dif  (~(diff dais base) bob)
          =/  mash     (~(mash dais base) [her sud ali-dif] [our syd bob-dif])
          :-  path
          ?~  mash
            ~
          `[mark (~(pact dais base) u.mash)]
        =/  [annotated=(list [path *]) unnotated=(list [path *])]
          (skid notations |=([* v=*] ?=(^ v)))
        =/  tic=desk  (cat 3 syd '-scratch')
        =/  tan=(list tank)
          %-  zing
          ^-  (list (list tank))
          :~  %-  tape-to-tanks
              """
              done setting up scratch space in {<[tic]>}
              please resolve the following conflicts and run
              |merge {<syd>} our {<[tic]>}
              """
              %^  tanks-if-any
                "annotated conflicts in:"  (turn annotated head)
              ""
              %^  tanks-if-any
                "unannotated conflicts in:"  (turn unnotated head)
              """
              some conflicts could not be annotated.
              for these, the scratch space contains
              the most recent common ancestor of the
              conflicting content.
              """
          ==
        =<  win
        %-  blab:(spam tan)
        :_  ~
        :*  %pass  /kiln/[syd]  %arvo  %c
            %info
            tic  %&
            %+  murn  notations
            |=  [=path dif=(unit [=mark =vase])]
            ^-  (unit [^path miso])
            ?~  dif
              ~
            `[path %mut mark.u.dif vase.u.dif]
        ==
      =+  "failed to merge with strategy meld"
      lose:(spam leaf+- >p.p.are< q.p.are)
    ?:  ?=(%& -.are)
      =+  "merged with strategy {<gem>}"
      win:(spam leaf+- ?~(p.are ~ [>`(set path)`p.are< ~]))
    ?.  auto
      =+  "failed to merge with strategy {<gem>}"
      lose:(spam leaf+- >p.p.are< q.p.are)
    ?+    gem
      (spam leaf+"strange auto" >gem< ~)
    ::
        $init
      =+  :-  "auto merge failed on strategy %init"
          "I'm out of ideas"
      lose:(spam leaf+-< leaf+-> [>p.p.are< q.p.are])
    ::
        $fine
      ?.  ?=($bad-fine-merge p.p.are)
        =+  "auto merge failed on strategy %fine"
        lose:(spam leaf+- >p.p.are< q.p.are)
      =>  (spam leaf+"%fine merge failed, trying %meet" ~)
      perform(gem %meet)
    ::
        $meet
      ?.  ?=($meet-conflict p.p.are)
        =+  "auto merge failed on strategy %meet"
        lose:(spam leaf+- >p.p.are< q.p.are)
      =>  (spam leaf+"%meet merge failed, trying %mate" ~)
      perform(gem %mate)
    ::
        $mate
      ?.  ?=($mate-conflict p.p.are)
        =+  "auto merge failed on strategy %mate"
        lose:(spam leaf+- >p.p.are< q.p.are)
      =>  .(gem %meld)
      =+  tic=(cat 3 syd '-scratch')
      =>  =+  :-  "%mate merge failed with conflicts,"
              "setting up scratch space at %{(trip tic)}"
          [tic=tic (spam leaf+-< leaf+-> q.p.are)]
      =.  ..mere  (fancy-merge tic our syd %init)
      =>  (spam leaf+"%melding %{(trip sud)} into scratch space" ~)
      %-  blab  :_  ~
      =/  note  [%merg (cat 3 syd '-scratch') her sud cas gem]
      [%pass /kiln/[syd] %arvo %c note]
    ==
  ::
  ++  tape-to-tanks
    |=  a/tape  ^-  (list tank)
    (scan a (more (just '\0a') (cook |=(a/tape leaf+a) (star prn))))
  ::
  ++  tanks-if-any
    |=  {a/tape b/(list path) c/tape}  ^-  (list tank)
    ?:  =(~ b)  ~
    (welp (tape-to-tanks "\0a{c}{a}") >b< ~)
  --
--