Docker entrypoint - fixes and error handling

Fixes a few stupid errors and improve the entrypoint to handle better the case where '/etc/duniter' is not a persistent volume.

And add a DEBUG_ENTRYPOINT boolean variable to enable set -x in the entrypoint.

release/docker/docker-entrypoint.sh

 #!/bin/sh
-
-home=/var/lib/duniter
-config=/etc/duniter
-home_default=$home/duniter_default
+set -u
 
 function boolean () {
   echo "$1" | sed -E 's/^(true|yes|1)$/true/i'
 }
+big_fat_warning='\033[01;31m**WARNING**:\033[0m'
+
+DEBUG_ENTRYPOINT="$(boolean "${DEBUG_ENTRYPOINT:-false}")"
+if [ "$DEBUG_ENTRYPOINT" = true ]; then
+  set -x
+fi
+
+home=/var/lib/duniter
+config=/etc/duniter
+home_default=$home/duniter_default
 
 manual_config="$(boolean "${DUNITER_MANUAL_CONFIG:-false}")"
 auto_sync="$(boolean "${DUNITER_AUTO_SYNC:-false}")"
 
-# Use path /etc/duniter/conf.json
-if ! [ -f "$config/conf.json" ] && [ -f "$home_default/conf.json" ]; then
-  mv "$home_default/conf.json" "$conf/conf.json"
+# Use new path /etc/duniter/conf.json
+if ! [ -f "$config/conf.json" ]; then
+  if [ "$(readlink "$home_default/conf.json")" = "$config/conf.json" ]; then
+    # The configuration file was moved already but the link is dangling
+    # It is likely that '/etc/duniter' is an anonymous volume
+    echo -e "$big_fat_warning Your configuration file didn't survive the restart!"
+    echo -e "$big_fat_warning Make sure that '/etc/duniter' is explicitely mounted as a persistent volume or you'll lose it again."
+    if [ -f "$home_default/conf.json.backup" ]; then
+      echo -e "$big_fat_warning Found backup file '$home_default/conf.json.backup'; using it..."
+      mv "$home_default/conf.json.backup" "$home_default/conf.json"
+    fi
+  fi
+  if [ -f "$home_default/conf.json" ]; then
+    echo "Moving existing configuration file '$home_default/conf.json' to its new location: '$config/conf.json'"
+    echo "A backup is kept at '$home_default/conf.json.backup'"
+    cp "$home_default/conf.json" "$home_default/conf.json.backup"
+    mv "$home_default/conf.json" "$config/conf.json"
+  fi
 fi
 mkdir -p "$home/duniter_default"
 ln -fs "$config/conf.json" "$home_default/conf.json"
@@ -55,11 +77,11 @@ fi
 if [ "$auto_sync" = true ]; then
   if ! [ -d "$home_default/data" ]; then
     echo "No 'data' folder. "
-    if [ -z "$DUNITER_SYNC_HOST" ]; then
+    if [ -z "$DUNITER_SYNC_HOST:-" ]; then
       echo "DUNITER_SYNC_HOST undefined. Can't start synchronization!"
     else
       echo "Starting synchronization..."
-      /usr/bin/duniter --home "$home" sync "$DUNITER_SYNC_HOST"
+      /usr/bin/duniter sync "$DUNITER_SYNC_HOST"
     fi
   fi
 fi