Update config_spec.md
Specify the logic `and` and `or` in file matching.
See
@@ -149,13 +149,17 @@ See also: [input filename matching guide](./filename_matching.html)
###### `filename_contains`
Keywords used to match filenames.
The matched keywords will be removed, and the remaining part is used as
-subject name (for loading corresponding images across modalities).
+subject name (for loading corresponding images across modalities). Note
+that if the type pf `filename_contains` is a string array, then a filename
+has to contain every string in the array to be a match.
See also: [input filename matching guide](./filename_matching.html)
###### `filename_not_contains`
Keywords used to exclude filenames.
-The filenames with these keywords will not be used as input.
+The filenames with these keywords will not be used as input. Note that
+if the type of `filename_not_contains` is a string array, then a filename
+must not contain any of the strings inthe array to be a match.
See also: [input filename matching guide](./filename_matching.html)
