support more general sig loading in sig overlap

src/sourmash/sig/__main__.py

@@ -384,12 +384,23 @@ def overlap(args):
 
     moltype = sourmash_args.calculate_moltype(args)
 
-    sig1 = sourmash.load_one_signature(
+    sig1 = sourmash.load_file_as_signatures(
         args.signature1, ksize=args.ksize, select_moltype=moltype
     )
-    sig2 = sourmash.load_one_signature(
+    sig1 = list(sig1)
+    if len(sig1) != 1:
+        notify(f"ERROR: 'sig overlap' needs exactly one signature per file; found {len(sig1)} in '{args.signature1}'")
+        sys.exit(-1)
+    sig2 = sourmash.load_file_as_signatures(
         args.signature2, ksize=args.ksize, select_moltype=moltype
     )
+    sig2 = list(sig2)
+    if len(sig2) != 1:
+        notify(f"ERROR: 'sig overlap' needs exactly one signature per file; found {len(sig2)} in '{args.signature2}'")
+        sys.exit(-1)
+
+    sig1 = sig1[0]
+    sig2 = sig2[0]
 
     notify(f"loaded one signature each from {args.signature1} and {args.signature2}")
 

tests/test_cmd_signature.py

@@ -3839,8 +3839,8 @@ def test_sig_describe_3_manifest_fails_when_moved(runtmp):
         runtmp.sourmash("sig", "describe", "mf.csv")
 
 
-@utils.in_tempdir
-def test_sig_overlap(c):
+def test_sig_overlap(runtmp):
+    c = runtmp
     # get overlap details
     sig47 = utils.get_test_data("47.fa.sig")
     sig63 = utils.get_test_data("63.fa.sig")
@@ -3857,6 +3857,24 @@ def test_sig_overlap(c):
     assert "number of hashes in common:  2529" in out
 
 
+def test_sig_overlap_2(runtmp):
+    c = runtmp
+    # get overlap details
+    sig47 = utils.get_test_data("47.fa.sig.zip")
+    sig63 = utils.get_test_data("63.fa.sig.zip")
+    c.run_sourmash("sig", "overlap", sig47, sig63)
+    out = c.last_result.out
+
+    print(out)
+
+    # md5s
+    assert "09a08691ce52952152f0e866a59f6261" in out
+    assert "38729c6374925585db28916b82a6f513" in out
+
+    assert "similarity:                  0.32069" in out
+    assert "number of hashes in common:  2529" in out
+
+
 @utils.in_tempdir
 def test_import_export_1(c):
     # check to make sure we can import what we've exported!