revamped load-fzf and load-zellij

load-fzf

@@ -1,7 +1,21 @@
 #! /usr/bin/env bash
+# shellcheck disable=SC2034,SC1090
+# SC2034 variables appear unsued. export if used externally
+# - uneeded, as this checked whether script is sourced
+# SC1090 Can't follow non-constant source
 
-BASE_0="$(basename ${0#-})"
-BASE_SHELL="$(basename "$SHELL")"
+# Helper function
+is_sourced() {
+    if [ -n "$ZSH_VERSION" ]; then 
+        case $ZSH_EVAL_CONTEXT in *:file:*) return 0;; esac
+    else  # Add additional POSIX-compatible shell names here, if needed.
+        case ${0##*/} in dash|-dash|bash|-bash|ksh|-ksh|sh|-sh) return 0;; esac
+    fi
+    return 1; # NOT sourced.
+}
+
+BASE_0=${BASE_0:-$0}
+BASE_SHELL=$(basename "$SHELL")
 
 if [[ "$1" == "--force" ]]; then
     [[ -e ~/.local/bin/fzf ]] && rm ~/.local/bin/fzf
@@ -12,11 +26,12 @@ fi
 if [[ -z "$(type -t fzf)" || ! -e "$(type -p fzf)" ]]; then
     curl -sS https://webi.sh/fzf | bash >&2
 
+    # shellcheck disable=SC2016 # $ inside single quotes is intentional
     printf '%s\n' \
     	'Run the following and then try again:' \
 	'    exec $SHELL -l' \
 	'' >&2
-elif [[ -z "${BASE_0}" || "${BASE_0}" == "$BASE_SHELL" ]]; then
+elif is_sourced; then
 
     FZF_CTRL_T_COMMAND="command find -L . -xdev -mindepth 1 \\( \
         -path '*/\\.*' \
@@ -28,6 +43,9 @@ elif [[ -z "${BASE_0}" || "${BASE_0}" == "$BASE_SHELL" ]]; then
     -o -type l -print 2> /dev/null | cut -b3- \
     "
 
+    # shellcheck disable=SC2034
+    # variable appears unsued. export if used externally
+    # - uneeded, as script is sourced
     FZF_ALT_C_COMMAND="command find -L . -xdev -mindepth 1 \\( \
         -path '*/\\.*' \
             -xdev \