Export mode for use in scripting keybindings

[joelim-work]

Related:

• Export cmdprefix for use in scripting #1579
• add auto-autocompletion of commands #1507

For certain keybindings, it can be useful to modify the behavior based on what mode lf is currently in. Right now there is no way to track the current mode except for using user-defined variables, which is more complex and error-prone.

Examples:

Using filter to select and open a file:

set incfilter

map f filter

cmap <enter> &{{
    # select and open file
    if [ "$lf_mode" = "filter" ]; then
        lf -remote "send $id :cmd-enter; setfilter; open"
    else
        lf -remote "send $id cmd-enter"
    fi
}}

cmap <a-n> &{{
    # go to next file
    if [ "$lf_mode" = "filter" ]; then
        lf -remote "send $id down"
    fi
}}

cmap <a-p> &{{
    # go to previous file
    if [ "$lf_mode" = "filter" ]; then
        lf -remote "send $id up"
    fi
}}

Expand partially-typed commands before executing them (e.g. type :del as a shorthand for :delete):

cmap <enter> &{{
    if [ "$lf_mode" = "command" ]; then
        lf -remote "send $id complete-cmd"
    else
        lf -remote "send $id cmd-enter"
    fi
}}

cmd complete-cmd :{{
    # position cursor at the end of the first word
    cmd-home
    cmd-word

    # perform tab completion before running the command
    cmd-complete
    cmd-enter
}}