BF: for datalad 0.10.0 - check/populate .gitattributes correctly

now that .gitattributes has some pre-populated by datalad settings we
cannot just check for its existence, we need to check if any particular line
is already defined

Author: yarikoptic

heudiconv/external/dlad.py

@@ -63,17 +63,30 @@ def add_to_datalad(topdir, studydir, msg, bids):
         assert ds.is_installed()
         superds = ds
 
-    create_file_if_missing(
-        op.join(studydir, '.gitattributes'),
-        """\
+    # TODO: we need a helper (in DataLad ideally) to ease adding such
+    # specifications
+    gitattributes_path = op.join(studydir, '.gitattributes')
+    # We will just make sure that all our desired rules are present in it
+    desired_attrs = """\
 * annex.largefiles=(largerthan=100kb)
 *.json annex.largefiles=nothing
 *.txt annex.largefiles=nothing
 *.tsv annex.largefiles=nothing
 *.nii.gz annex.largefiles=anything
 *.tgz annex.largefiles=anything
 *_scans.tsv annex.largefiles=anything
-""")
+"""
+    if op.exists(gitattributes_path):
+        with open(gitattributes_path, 'rb') as f:
+            known_attrs = [line.decode('utf-8').rstrip() for line in f.readlines()]
+    else:
+        known_attrs = []
+    for attr in desired_attrs.split('\n'):
+        if attr not in known_attrs:
+            known_attrs.append(attr)
+    with open(gitattributes_path, 'wb') as f:
+        f.write('\n'.join(known_attrs).encode('utf-8'))
+
     # so for mortals it just looks like a regular directory!
     if not ds.config.get('annex.thin'):
         ds.config.add('annex.thin', 'true', where='local')