Add new `functions` flag -V/--inherit-variable

--inherit-variable takes a variable name and snapshots its current
value. When the function is executed, it will have a local variable with
this value already defined. Printing the function source will include
synthesized `set -l` lines for the values.

This is primarily useful for functions that are created on the fly, such
as in `psub`.

1 files changed, 0 insertions, 0 deletions

diff --git a/tests/function.err b/tests/function.err
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/tests/function.err