papis: Add ability to show tag counts to papis-tags

The `papis tags` command is extended with the functionality to not
just display all tags used in current query, sorted alphabetically,
but also to display how often they appear.

Use `papis tags -c` to show a space-separated count of how often
each tag is used next to the tag name, in descending order.

writing/.config/papis/scripts/papis-tags

@@ -14,7 +14,10 @@ from papis.database.base import Database
 from papis.document import Document
 
 parser = argparse.ArgumentParser()
-parser.add_argument("query", nargs="*", help="the query to search for")
+parser.add_argument(
+    "--count", "-c", help="the query to search for", action="store_true"
+)
+parser.add_argument("query", nargs="*", help="the query to search for", default="*")
 args = parser.parse_args()
 
 
@@ -22,7 +25,7 @@ def main(db: Database, args) -> None:
     query = " ".join(args.query)
     docs: list[Document] = db.query(query)
 
-    all_tags: set[str] = set()
+    all_tags: dict[str, int] = {}
     for doc in docs:
         t: list[str] | str = doc.get("tags", "")
         tags = (
@@ -30,10 +33,25 @@ def main(db: Database, args) -> None:
         )
 
         for tag in tags:
-            all_tags.add(tag)
+            if tag == '':
+                continue
+            all_tags[tag] = all_tags.get(tag, 0) + 1
 
+    if args.count:
+        print_tags_and_counts(all_tags)
+    else:
+        print_tags_only(all_tags)
+
+def print_tags_only(all_tags):
     for tag in sorted(all_tags):
         print(tag)
 
+def print_tags_and_counts(all_tags):
+    for tag, count in sorted(all_tags.items(), key=lambda d: d[1], reverse=True):
+        if args.count:
+            print(tag, count)
+        else:
+            print(tag)
+
 if __name__ == "__main__":
     main(database.get(), args)