add automatic README.md update

Makefile

@@ -119,6 +119,14 @@ publish:
 		docker push $$image; \
 	done
 
+#Update README.md based on the template ._README.md
+TOOLSET := `echo "$(sort $(IMAGES_TO_PUBLISH))" | sed -e "s/ /\n - /g"))`
+README_HEAD = `cat ./_README.md | sed -e 's/%CONTAINERS_LIST%.*//g'`
+README_TAIL = `cat ./_README.md | sed -e '1,/%CONTAINERS_LIST%/d'`
+
+update_readme:
+	@echo "$(README_HEAD)\n - $(TOOLSET) $(README_TAIL)" | sed -e "s/%LAST_UPDATE%/\n_Last update: `date`_ \n/g" > README.md
+
 delete_dangling_images:
 	@echo "Removing dangling images"
 	@docker image prune -f
@@ -126,6 +134,7 @@ help:
 	@echo -e "make [all] \n\t # Creates all the images"
 	@echo -e "make <TARGET> \n\t # Creates an specific image"
 	@echo -e "make publish \n\t # Push the images to the UNL registry"
+	@echo -e "make update_readme \n\t Update the README.md file"
 #	@echo -e "make security \n\t # Send the images to Tenable. Use env variables TENABLE_IO_ACCESS_KEY and TENABLE_IO_SECRET_KEY"
 
 debug:

_README.md

+[![pipeline status](https://git.unl.edu/unl-its/docker-ci/badges/develop/pipeline.svg)](https://git.unl.edu/unl-its/docker-ci/commits/develop)
+
+# Docker-ci
+
+## Containers usefull in CI process
+
+### Building Images
+
+To build these images, clone this repository onto a machine with docker and make installed. Run `make` and all of the images will be built and installed as local docker images.  
+This file is automatically updated after execute `git commit` based on the content of file `_README.md` 
+
+### Tools available:
+
+%CONTAINERS_LIST%
+
+%LAST_UPDATE%
+