add --kexec paramter to specify custom image

nixos-remote

@@ -14,6 +14,8 @@ Options:
   pass value to nix-build. can be used to set disk-names for example
 * --argstr name value
   pass value to nix-build as string
+* --kexec url
+  use another kexec tarball to bootstrap NixOS
 USAGE
 }
 
@@ -23,6 +25,7 @@ abort() {
 }
 
 nix_args=()
+kexec_url=https://github.com/nix-community/nixos-images/releases/download/nixos-22.05/nixos-kexec-installer-x86_64-linux.tar.gz
 
 while [[ $# -gt 0 ]]; do
   case "$1" in
@@ -39,6 +42,10 @@ while [[ $# -gt 0 ]]; do
       showUsage
       exit 0
       ;;
+    --kexec)
+      kexec_url=$2
+      shift
+      ;;
     *)
       if [ -z ${ssh_connection+x} ]; then
         ssh_connection=$1
@@ -80,7 +87,7 @@ fetch(){
 }
 rm -rf /root/kexec
 mkdir -p /root/kexec
-fetch https://github.com/nix-community/nixos-images/releases/download/nixos-22.05/nixos-kexec-installer-x86_64-linux.tar.gz | tar -C /root/kexec -xvzf-
+fetch "$kexec_url" | tar -C /root/kexec -xvzf-
 export TMPDIR=/root/kexec
 setsid /root/kexec/kexec/run
 SSH