Fix multideploy MULTIDEPLOY_FILENAME conf read and allow an absolute path

_getdeployconf assigns and exports the variable, it does not print the
value, so wrapping it in a command substitution ran it in a subshell and
always yielded an empty string. A MULTIDEPLOY_FILENAME saved by an
earlier run was therefore never restored on renewal and the hook
silently fell back to multideploy.yml. Call it the same way every other
deploy hook does.

Also treat a MULTIDEPLOY_FILENAME starting with '/' as an absolute path
instead of always resolving it under DOMAIN_PATH, so one deploy file can
live outside the certificate directory and be shared by all domains.
Names without a leading '/' keep resolving under DOMAIN_PATH as before.

deploy/multideploy.sh

@@ -10,6 +10,10 @@
 # Usage (shown values are the examples):
 # 1. Set optional environment variables
 #   - export MULTIDEPLOY_FILENAME="multideploy.yaml"     - "multideploy.yml" will be automatically used if not set"
+#     A name without a leading '/' is looked up in the certificate directory
+#     of the domain. An absolute path is used as is, so a single deploy file
+#     can be shared by all domains, e.g.
+#   - export MULTIDEPLOY_FILENAME="/etc/acme/multideploy.yml"
 #
 # 2. Run command:
 # acme.sh --deploy --deploy-hook multideploy -d example.com
@@ -49,7 +53,7 @@ multideploy_deploy() {
   _debug _cfullchain "$_cfullchain"
   _debug _cpfx "$_cpfx"
 
-  MULTIDEPLOY_FILENAME="${MULTIDEPLOY_FILENAME:-$(_getdeployconf MULTIDEPLOY_FILENAME)}"
+  _getdeployconf MULTIDEPLOY_FILENAME
   if [ -z "$MULTIDEPLOY_FILENAME" ]; then
     MULTIDEPLOY_FILENAME="multideploy.yml"
     _info "MULTIDEPLOY_FILENAME is not set, so I will use 'multideploy.yml'."
@@ -75,7 +79,8 @@ multideploy_deploy() {
 #   This function preprocesses the deploy file by checking if 'yq' is installed,
 #   verifying the existence of the deploy file, and ensuring only one deploy file is present.
 # Arguments:
-#   $@ - Posible deploy file names.
+#   $@ - Posible deploy file names. A name starting with '/' is treated as an
+#        absolute path, any other name is relative to the domain directory.
 # Usage:
 #   _preprocess_deployfile "<deploy_file1>" "<deploy_file2>?"
 _preprocess_deployfile() {
@@ -87,15 +92,21 @@ _preprocess_deployfile() {
   _debug3 "yq is installed."
 
   # Check if deploy file exists
+  found_file=""
   for file in "$@"; do
-    _debug3 "Checking file" "$DOMAIN_PATH/$file"
-    if [ -f "$DOMAIN_PATH/$file" ]; then
+    if _startswith "$file" "/"; then
+      _multideploy_path="$file"
+    else
+      _multideploy_path="$DOMAIN_PATH/$file"
+    fi
+    _debug3 "Checking file" "$_multideploy_path"
+    if [ -f "$_multideploy_path" ]; then
       _debug3 "File found"
       if [ -n "$found_file" ]; then
         _err "Multiple deploy files found. Please keep only one deploy file."
         return 1
       fi
-      found_file="$file"
+      found_file="$_multideploy_path"
     else
       _debug3 "File not found"
     fi
@@ -105,12 +116,12 @@ _preprocess_deployfile() {
     _err "Deploy file not found. Go to https://github.com/acmesh-official/acme.sh/wiki/deployhooks#36-deploying-to-multiple-services-with-the-same-hooks to see how to create one."
     return 1
   fi
-  if ! _check_deployfile "$DOMAIN_PATH/$found_file"; then
-    _err "Deploy file is not valid: $DOMAIN_PATH/$found_file"
+  if ! _check_deployfile "$found_file"; then
+    _err "Deploy file is not valid: $found_file"
     return 1
   fi
 
-  echo "$DOMAIN_PATH/$found_file"
+  echo "$found_file"
 }
 
 # Description: