feat: add option to read variables from file

build/start-container.sh

@@ -1,17 +1,48 @@
 #! /usr/bin/env sh
 
+if [ -n "${SMTP_HOST_FILE}" ]; then
+    SMTP_HOST=$cat ${SMTP_HOST_FILE});
+fi
+
+if [ -n "${SMTP_PORT_FILE}" ]; then
+    SMTP_PORT=$(cat ${SMTP_PORT_FILE});
+fi
+
+if [ -n "${SMTP_FROM_FILE}" ]; then
+    SMTP_FROM=$(cat ${SMTP_FROM_FILE});
+fi
+
+if [ -n "${SMTP_USER_FILE}" ]; then
+    SMTP_USER=$(cat ${SMTP_USER_FILE});
+fi
+
+if [ -n "${SMTP_PASSWORD_FILE}" ]; then
+    SMTP_PASSWORD=$(cat ${SMTP_PASSWORD_FILE});
+fi
+
+if [ -n "${EMAIL_FILE}" ]; then
+    EMAIL=$(cat ${EMAIL_FILE});
+else
+    if [ -n "${EMAIL}" ]; then
+        EMAIL="To: ${TO_ADDRESS}\nSubject: ${SUBJECT}\n\n${MESSAGE}";
+    fi
+fi
+
+if [ -n "${MSMTP_CONFIG_FILE}" ]; then
+    MSMTP_CONFIG_FILE="~/.msmtprc"
+    touch ${MSMTP_CONFIG_FILE}
+    chmod 600 ${MSMTP_CONFIG_FILE}
     echo "defaults
-auth on
+    auth ${SMTP_AUTH:-on}
-tls on
+    tls ${SMTP_TLS:-on}
 
     account default
     host ${SMTP_HOST}
-port ${SMTP_PORT}
+    port ${SMTP_PORT:-587}
-tls_starttls ${SMTP_STARTTLS}
+    tls_starttls ${SMTP_STARTTLS:-on}
     from ${SMTP_FROM}
     user ${SMTP_USER}
-password ${SMTP_PASSWORD}" > ~/.msmtprc
+    password ${SMTP_PASSWORD}" > ${MSMTP_CONFIG_FILE}
+fi
 
-chmod 600 ~/.msmtprc
+echo -e "${EMAIL}" | msmtp --read-recipients -C ${MSMTP_CONFIG_FILE}
-
-echo -e "Subject: ${SUBJECT}\n\n${MESSAGE}" | msmtp ${TO_ADDRESS}