Implemented docker-entrypoint.sh and moved some contents from Dockerfile into the docker-entrypoint.sh script

Dockerfile

@@ -5,15 +5,8 @@ LABEL org.opencontainers.image.authors="bluefox@privacynerd.de"
 
 WORKDIR /
 
+COPY docker-entrypoint.sh /docker-entrypoint.sh
 RUN apk update --no-cache && \
-    apk add --no-cache git && \
-    adduser -g cronuser -s /bin/sh -H -D cronuser && \
-    mkdir crond logs && \
-    touch logs/crond.log logs/puller.log && \
-    chown cronuser logs -R && \
-    echo $'#!/bin/sh\ncd /to-pull && git pull' > puller.sh && \
-    echo $'* * * * * cronuser /puller.sh\n' > crond/cronuser && \
-    chmod +x puller.sh
+    apk add --no-cache git
 
-ENTRYPOINT ["docker-entrypoint.sh"]
-CMD ["crond", "-f", "-c", "crond"]
+ENTRYPOINT ["/docker-entrypoint.sh"]

docker-entrypoint.sh

@@ -1,3 +1,95 @@
-#!/bin/bash
+#!/bin/sh
+
+runningUserID="$(id -u)"
+if [ ! "$runningUserID" -eq 0 ]; then
+	echo "docker-entrypoint.sh needs to be run as root, exiting..."
+	exit 1
+fi
 
 
+# set the PULL_LOCATION env var if not set already
+if [ -z "$PULL_LOCATION" ]; then  # if the env var is not set, set the default
+	PULL_LOCATION="/to-pull"
+	echo "PULL_LOCATION environment variable not set. Defaulting to /to-pull"
+fi
+if [ ! -d "$PULL_LOCATION" ]; then  # if the folder to pull does not exist
+	echo "'$PULL_LOCATION' does not exist, exiting..."
+	exit 1
+fi
+
+
+# check if PULL_LOCATION is a valid git repo
+git config --global --add safe.directory "$PULL_LOCATION"  # make git trust this folder to check if it is a repo
+current_dir=$PWD; cd "$PULL_LOCATION"; is_git_repo="$(git rev-parse --is-inside-work-tree 2>/dev/null)"; cd "$current_dir";
+if [ ! "$is_git_repo" ]; then
+	echo "'$PULL_LOCATION' is no git repository, exiting..."
+	exit 1
+fi
+
+
+# Some PULL_INTERVAL env var checks
+# check if the var is even set; and if it is set, check if it is an integer
+# integer check found here: https://www.baeldung.com/linux/bash-variable-is-numeric 
+if [ -z "$PULL_INTERVAL" ]; then
+	PULL_INTERVAL=60  # every minute by default
+	echo "PULL_INTERVAL environment variable not set. Defaulting to [every] 60 [seconds]"
+fi
+if [[ ! "$PULL_INTERVAL" =~ '^[0-9]+([.][0-9]+)?$' ]]; then
+	PULL_INTERVAL=60
+	echo "PULL_INTERVAL must be an integer, defaulting to [every] 60 [seconds] now"
+fi
+if [ "$PULL_INTERVAL" -lt 5 ]; then  # if the PULL_INTERVAL is too low (more than every 5 seconds)
+	echo "PULL_INTERVAL must not be lower than 5 (every 5 seconds). Now set to 5."
+	PULL_INTERVAL=5
+fi
+
+
+# now the user management (for permissions, security)
+if [ -z "$PULLER_UID" ]; then 
+	PULLER_UID=1000
+	echo "PULLER_UID environment variable has not been set, defaulting to 1000..."
+fi
+if [[ ! "$PULLER_UID" =~ '^[0-9]+([.][0-9]+)?$' ]]; then  # check that PULLER_UID is a number
+        PULLER_UID=1000  # set to roots uid
+        echo "PULLER_UID must be an integer, defaulting to 1000 now."
+fi
+if [ ! "$PULLER_UID" = "0" ]; then
+	# create a new user (for running the git pull; for security reasons)
+	adduser -g gitpuller -s /bin/sh -u $PULLER_UID -D gitpuller  # user needs home dir for git config (see below)
+	echo "Added user 'gitpuller' with UID $PULLER_UID"
+	PULLER_USER="gitpuller"
+	su $PULLER_USER -c "cd $PULL_LOCATION; git config --global --add safe.directory '$PULL_LOCATION';"
+else
+	PULLER_USER="root"
+	# no need for git config ... as this is already done for the root user (see 'check if PULL_LOCATION is a valid git repo')
+fi
+
+#print log size info
+if [ "$GIT_OUTPUT" = "0" ]; then
+	echo "Not logging git outputs exept those to stderr (reducing the log size)"
+else
+	echo "INFO: logging all git outputs; you can reduce log size by setting the env var GIT_OUTPUT to 0"
+fi
+
+echo ""
+echo "-----"
+echo "Starting docker-git-puller with '$PULL_LOCATION' as the pull location."
+echo "Pulling every $PULL_INTERVAL seconds."
+echo "-----"
+echo ""
+
+
+
+while true; do
+	# if $GIT_OUTPUT is 0, do not write the 'git pull' output to stdout; for any other value, do it
+	if [ "$GIT_OUTPUT" = "0" ]; then
+		su $PULLER_USER -c "cd $PULL_LOCATION; git pull > /dev/null;"
+	else
+		echo "[$(date)] Pulling git repo..."
+		su $PULLER_USER -c "cd $PULL_LOCATION; git pull"
+		echo "Waiting $PULL_INTERVAL seconds for next pull"
+		echo "-----"
+		echo ""
+	fi
+	sleep $PULL_INTERVAL
+done