support/scripts/mkusers: preserve group members

When the function add_one_group is called on an existing group,
make sure the members of this group are not removed in the process of
deleting then re-adding the group.

Signed-off-by: Johan Oudinet <johan.oudinet@gmail.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
[Thomas: add curly braces when referencing ${members}, as suggested by
Yann.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

(cherry picked from commit 497f7134fca4b111499b2fd23501d7e048303e7c)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

support/scripts/mkusers

@@ -75,6 +75,14 @@ get_gid() {
         '$1 == group { printf( "%d\n", $3 ); }' "${GROUP}"
 }
 
+#----------------------------------------------------------------------------
+get_members() {
+    local group="${1}"
+
+    awk -F: -v group="${group}"                             \
+        '$1 == group { printf( "%s\n", $4 ); }' "${GROUP}"
+}
+
 #----------------------------------------------------------------------------
 get_username() {
     local uid="${1}"
@@ -211,16 +219,17 @@ generate_gid() {
 add_one_group() {
     local group="${1}"
     local gid="${2}"
-    local _f
+    local members
 
     # Generate a new GID if needed
     if [ ${gid} -eq -1 ]; then
         gid="$( generate_gid "${group}" )"
     fi
 
+    members=$(get_members "$group")
     # Remove any previous instance of this group, and re-add the new one
     sed -i --follow-symlinks -e '/^'"${group}"':.*/d;' "${GROUP}"
-    printf "%s:x:%d:\n" "${group}" "${gid}" >>"${GROUP}"
+    printf "%s:x:%d:%s\n" "${group}" "${gid}" "${members}" >>"${GROUP}"
 
     # Ditto for /etc/gshadow if it exists
     if [ -f "${GSHADOW}" ]; then