add procedure to configure non-annexing of docker metadata

datalad_container/resources/procedures/cfg_containers.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+"""Procedure to configure dataset for containers
+"""
+
+import sys
+
+from datalad.distribution.dataset import require_dataset
+from datalad.support import path as op
+
+ds = require_dataset(
+    sys.argv[1],
+    check_installed=True,
+    purpose='Containers dataset configuration')
+
+# unless taken care of by the template already, each item in here
+# will get its own .gitattributes entry to keep it out of the annex
+# give relative path to dataset root (use platform notation)
+force_in_git = [
+    'environments/**/*.json',
+    'environments/*/image/repositories',
+]
+# make an attempt to discover the prospective change in .gitattributes
+# to decide what needs to be done, and make this procedure idempotent
+# (for simple cases)
+attr_fpath = op.join(ds.path, '.datalad', '.gitattributes')
+if op.lexists(attr_fpath):
+    with open(attr_fpath, 'rb') as f:
+        attrs = f.read().decode()
+else:
+    attrs = ''
+
+# amend gitattributes, if needed
+ds.repo.set_gitattributes([
+    (path, {'annex.largefiles': 'nothing'})
+    for path in force_in_git
+    if '{} annex.largefiles=nothing'.format(path) not in attrs
+], attrfile=attr_fpath)
+
+# leave clean
+ds.save(
+    path=[attr_fpath],
+    message="Apply default containers dataset setup",
+    to_git=True,
+)