Allow to specify OpenStructure base image in bump_version script

container/Dockerfile

-ARG OPENSTRUCTURE_VERSION="2.0.0-bionic"
-FROM registry.scicore.unibas.ch/schwede/openstructure:${OPENSTRUCTURE_VERSION}
+ARG OPENSTRUCTURE_IMAGE_TAG="2.0.0-bionic"
+FROM registry.scicore.unibas.ch/schwede/openstructure:${OPENSTRUCTURE_IMAGE_TAG}
 
 # ARGUMENTS
 ###########

scripts/bump-version.py

 #!/usr/bin/env python
 import sys
 
-if len(sys.argv) < 3:
-  print("USAGE: python scripts/bump-version.py PM3_VERSION OST_VERSION")
+if len(sys.argv) < 4:
+  print("USAGE: python scripts/bump-version.py PM3_VERSION OST_VERSION OST_DOCKER_IMAGE_TAG")
   print("-> *_VERSION format is MAJOR.MINOR.PATCH (e.g. 1.9.1)")
   print("-> assumption is that git tags will exist for those *_VERSION")
+  print("-> OST_DOCKER_IMAGE_TAG refers to the image in the OpenStructure")
+  print("   Docker registry from which the ProMod3 image will bootstrap")
   sys.exit(1)
 
 # split up version number
@@ -12,6 +14,7 @@ version_string = sys.argv[1]
 version = version_string.split('.')
 major, minor, patch = (int(version[0]), int(version[1]), int(version[2]))
 ost_version_string = sys.argv[2]
+ost_docker_image_tag = sys.argv[3]
 
 # fix CMakeLists
 lines = open("CMakeLists.txt").readlines()
@@ -36,8 +39,8 @@ open("CHANGELOG", "w").writelines(lines)
 # fix Docker recipe
 lines = open("container/Dockerfile").readlines()
 for i, line in enumerate(lines):
-  if line.startswith("ARG OPENSTRUCTURE_VERSION"):
-    lines[i] = 'ARG OPENSTRUCTURE_VERSION="%s"\n' % ost_version_string
+  if line.startswith("ARG OPENSTRUCTURE_IMAGE_TAG"):
+    lines[i] = 'ARG OPENSTRUCTURE_IMAGE_TAG="%s"\n' % ost_docker_image_tag
   elif line.startswith("ARG PROMOD_VERSION"):
     lines[i] = 'ARG PROMOD_VERSION="%s"\n' % version_string
 open("container/Dockerfile", "w").writelines(lines)
@@ -48,7 +51,7 @@ lines = open(vfile).readlines()
 for i, line in enumerate(lines):
   if line.startswith("From: registry.scicore.unibas.ch/schwede/promod3:"):
     lines[i] = 'From: registry.scicore.unibas.ch/schwede/promod3:'+\
-      '%s' % version_string
+      '%s-OST%s\n' % (version_string, ost_docker_image_tag)
     break
 open(vfile, "w").writelines(lines)