cram: Add filter-query-and-exclude-ambiguous-dates-by test

Shows the interaction between the query and exclude-ambiguous-dates-by
options. This test currently passes on master (as of 1d92f6d)
but fails on the victorlin/revert-pandas-query-variable-extraction branch
(as of 5907992).

tests/functional/filter/cram/filter-query-and-exclude-ambiguous-dates-by.t

@@ -0,0 +1,26 @@
+Setup
+
+  $ source "$TESTDIR"/_setup.sh
+
+Create metadata TSV file for testing.
+
+  $ cat >metadata.tsv <<~~
+  > strain	date	region
+  > SEQ_1	2020	Asia
+  > SEQ_2	2020	Asia
+  > SEQ_3	2020	Asia
+  > SEQ_4	2020	North America
+  > ~~
+
+Confirm that `--exclude-ambiguous-dates-by` works for all year only ambiguous dates.
+
+  $ ${AUGUR} filter \
+  >  --metadata metadata.tsv \
+  >  --query 'region=="Asia"' \
+  >  --exclude-ambiguous-dates-by any \
+  >  --empty-output-reporting silent \
+  >  --output-strains filtered_strains.txt
+  4 strains were dropped during filtering
+  \t1 of these were filtered out by the query: "region=="Asia"" (esc)
+  \t3 of these were dropped because of their ambiguous date in any (esc)
+  0 strains passed all filters