It's currently too easy for someone to bork their shell by doing something
like `function test; return 0; end`. That's obviously a silly, contrived,
example but the point is that novice users who learn about functions are
prone to do something like that without realizing it will bork the shell. Even
expert users who know about the `test` builtin might forget that, say, `pwd`
is a builtin.
This change adds a `--shadow-builtin` flag that must be specified to
indicate you know what you're doing.
Fixes#3000
I'm going to modify these functions as part of dealing with issue #3000
and don't want those changes to be masked by running the files through
`make style`.
The existing implementation grows the $dirprev array without bounds. Besides
causing what would appear to be a memory leak it also makes the nextd and
prevd commands more expensive than they need to be. It also makes it harder to
create a useful "menu" cd command.
In addition to implementing a reasonable limit on the size of the $dirprev
array I've reformatted the code using fish_indent.
Update the documentation to include mentions of the $dirprev and $dirnext
variables as well as the limit on how much directory history is kept.
Fixes 2836
