Modify read-secrets script to allow keeping values

If the SKIP_SET_VARIABLE_SECRET_OVERRIDE environment variable
is set, read-secrets.sh will not overwrite existing values by secrets.

README.md

@@ -65,6 +65,8 @@ RUN curl -o /tmp/read-secrets.sh "https://raw.githubusercontent.com/HSLdevcom/jo
 CMD /bin/bash -c "source /tmp/read-secrets.sh && java -jar /.../xxx.jar"
 ```
 
+If the SKIP_SET_VARIABLE_SECRET_OVERRIDE environment variable is set, pre-exisiting values will not be overriden by secrets.
+
 ### download-docker-bundle.sh
 
 Downloads and extract the latest version of the docker bundle. It uses the `gh` github command line tool to retrieve the bundle from the releases.

docker/read-secrets.sh

@@ -23,14 +23,20 @@ set -eu
 # FOO1=bar1
 # FOO2_BLABLA=bar2
 # FOO3_LOL=bar3.lolo
+#
+# If the $SKIP_SET_VARIABLE_SECRET_OVERRIDE environment variable is set, pre-exisiting values will not be overriden by secrets.
 
 # read docker secrets into environment variables
 SECRET_STORE_BASE_PATH="${SECRET_STORE_BASE_PATH:-/run/secrets}"
 for SECRET_FILENAME in $(ls "$SECRET_STORE_BASE_PATH");
 do
     # replace non-alphanumeric characters with _ and convert to uppercase
     VAR_NAME=$(echo $SECRET_FILENAME | sed -E 's/[^a-zA-Z0-9]+/_/g' | tr a-z A-Z)
-    VAR_VALUE=$(cat "$SECRET_STORE_BASE_PATH/$SECRET_FILENAME")
-    export "$VAR_NAME"="$VAR_VALUE"
-    echo "Found secret '$SECRET_FILENAME', exported it as '$VAR_NAME' environment variable."
+    if [ ! -z "$SKIP_SET_VARIABLE_SECRET_OVERRIDE" ] && [ ! -z "$(printenv $VAR_NAME)" ]; then
+        echo "Secret environment value override disabled. Used existing value for '$VAR_NAME' environment variable."
+    else
+        VAR_VALUE=$(cat "$SECRET_STORE_BASE_PATH/$SECRET_FILENAME")
+        export "$VAR_NAME"="$VAR_VALUE"
+        echo "Found secret '$SECRET_FILENAME', exported it as '$VAR_NAME' environment variable."
+    fi
 done