fish_history negates private mode

[etcusrvar]

fish 3.1.2
Linux 5.9.16 x86_64

According to the docs - "In private mode, old history is not available and any interactive commands you execute will not be appended to the global history file"

But when launching fish with both fish_history set and in private mode, private mode is ignored/overridden/negated.

$ d=$(mktemp -d)
$ cd $d
$ sh -c "env HOME=$d fish"
Welcome to fish, ...
x@x ~> foo
fish: Unknown command: foo
x@x ~ [127]> bar
fish: Unknown command: bar
x@x ~ [127]> history
bar
foo
x@x ~> exit

$ sh -c "env HOME=$d fish --private"
Welcome to fish, ...
fish is running in private mode, history will not be persisted.
x@x ~> history
x@x ~> exit

$ sh -c "env HOME=$d fish_history=default fish --private"
Welcome to fish, ...
fish is running in private mode, history will not be persisted.
x@x ~> history
history
bar
foo
x@x ~> baz
fish: Unknown command: baz
x@x ~ [127]> history
baz
history
bar
foo
x@x ~> exit

$ sh -c "env HOME=$d fish"
Welcome to fish, ...
x@x ~> history
baz
history
bar
foo

[ridiculousfish]

With 118f710, fish_private_mode and fish_history are distinct. If fish_private_mode is set, commands you run are stored in memory, and can be recalled via up-arrow, but are not written to disk. It can be dynamically toggled on and off by setting the fish_private_mode variable.