feat: allow setting DOCKER_BIN path for docker execution

This change allows operators to specify a DOCKER_BIN environment variable. This will specify a binary to run when executing docker, which is useful in cases where the 'docker' command being run must be modified in a way that would otherwise be invasive to Dokku, but minimalistic if done within a wrapper.

plugins/ps/internal-functions

@@ -61,7 +61,7 @@ cmd-ps-report-single() {
   local APP_CONTAINER_STATUS
   for CONTAINER_FILE in $CONTAINER_FILES; do
     CID=$(<"$DOKKU_ROOT/$APP/$CONTAINER_FILE")
-    APP_CONTAINER_STATUS=$(docker inspect -f '{{.State.Status}}' "$CID" 2>/dev/null || true)
+    APP_CONTAINER_STATUS=$("$DOCKER_BIN" inspect -f '{{.State.Status}}' "$CID" 2>/dev/null || true)
     [[ -z "$APP_CONTAINER_STATUS" ]] && APP_CONTAINER_STATUS="missing"
     STATUSES+=("${CONTAINER_FILE#*.}:$APP_CONTAINER_STATUS#${CID:0:12}")
   done

plugins/ps/subcommands/default

@@ -21,7 +21,7 @@ ps_main_cmd() {
     has_tty && local DOKKU_RUN_OPTS="-i -t"
     dokku_log_info1_quiet "running processes in container: $CID"
     # shellcheck disable=SC2086
-    docker exec $DOKKU_RUN_OPTS $CID /bin/sh -c "ps auxwww"
+    "$DOCKER_BIN" exec $DOKKU_RUN_OPTS $CID /bin/sh -c "ps auxwww"
   done
 }