[PATCH 2/2] bash-completion:fix shellcheck warning

[t . feng]

SC2207 (warning): Prefer mapfile or read -a to split
command output (or quote to avoid splitting).
SC2120 (warning): __grub_get_options_from_help references arguments,
but none are ever passed.
SC2155 (warning): Declare and assign separately to avoid
masking return values.

In grub-completion.bash.in line 56:
        COMPREPLY=($(compgen -P "${2-}" -W "${1-}" -S "${4-}" --
"$cur"))
                   ^-- SC2207 (warning)

In grub-completion.bash.in line 63:
__grub_get_options_from_help () {
^-- SC2120 (warning)

In grub-completion.bash.in line 115:
    local config_file=$(__grub_dir)/grub.cfg
          ^---------^ SC2155 (warning)

In grub-completion.bash.in line 119:
        COMPREPLY=( $(compgen \
                    ^-- SC2207 (warning)

In grub-completion.bash.in line 126:
    local grub_dir=$(__grub_dir)
          ^------^ SC2155 (warning)

In grub-completion.bash.in line 128:
    COMPREPLY=( $( compgen -f -X '!*/*.mod' -- "${grub_dir}/$cur" | {
                ^-- SC2207 (warning)

SC2120: the current code meets the exception and does not need to be
modified

ref:https://github.com/koalaman/shellcheck/wiki/SC2207
ref:https://github.com/koalaman/shellcheck/wiki/SC2120
ref:https://github.com/koalaman/shellcheck/wiki/SC2155

---
 .../bash-completion.d/grub-completion.bash.in | 40 ++++++++++++-------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/util/bash-completion.d/grub-completion.bash.in 
b/util/bash-completion.d/grub-completion.bash.in
index 93d143480..7449e629a 100644
--- a/util/bash-completion.d/grub-completion.bash.in
+++ b/util/bash-completion.d/grub-completion.bash.in
@@ -53,7 +53,10 @@ __grubcomp () {
         ;;
     *)
         local IFS=' '$'\t'$'\n'
-        COMPREPLY=($(compgen -P "${2-}" -W "${1-}" -S "${4-}" -- "$cur"))
+        COMPREPLY=()
+        while read -r line; do
+            COMPREPLY+=("${line}")
+        done < <(compgen -P "${2-}" -W "${1-}" -S "${4-}" -- "$cur")
         ;;
     esac
 }
@@ -112,28 +115,35 @@ __grub_get_last_option () {
 
 __grub_list_menuentries () {
     local cur="${COMP_WORDS[COMP_CWORD]}"
-    local config_file=$(__grub_dir)/grub.cfg
+    local config_file
+    config_file=$(__grub_dir)/grub.cfg
 
     if [ -f "$config_file" ];then
         local IFS=$'\n'
-        COMPREPLY=( $(compgen \
-            -W "$( awk -F "[\"']" '/menuentry/ { print $2 }' $config_file )" \
-            -- "$cur" )) #'# Help emacs syntax highlighting
+        COMPREPLY=()
+        while read -r line; do
+            COMPREPLY+=("${line}")
+        done < <(compgen \
+                -W "$( awk -F "[\"']" '/menuentry/ { print $2 }' $config_file 
)" \
+                -- "$cur" ) #'# Help emacs syntax highlighting
     fi
 }
 
 __grub_list_modules () {
-    local grub_dir=$(__grub_dir)
+    local grub_dir
+    grub_dir=$(__grub_dir)
     local IFS=$'\n'
-    COMPREPLY=( $( compgen -f -X '!*/*.mod' -- "${grub_dir}/$cur" | {
-         while read -r tmp; do
-             [ -n "$tmp" ] && {
-                 tmp=${tmp##*/}
-                 printf '%s\n' ${tmp%.mod}
-             }
-         done
-         }
-        ))
+    COMPREPLY=()
+    while read -r line; do
+        COMPREPLY+=("${line}")
+    done < <(compgen -f -X '!*/*.mod' -- "${grub_dir}/$cur" | {
+        while read -r tmp; do
+            [ -n "$tmp "] && {
+                tmp=${tmp##*/}
+                printf '%s\n' ${tmp%.mod}
+            }
+        done
+    })
 }
 
 #
-- 
2.27.0