Prevent toot timeline to break when piped to extenal programs

Toot timeline try to ask the user to continue in the next page. This
doesn't works if the command is piped to any other software.

We stop the query in the first loop when not in a tty context. The
command should be called with the expected item count in this case.

changelog.yaml

@@ -3,6 +3,7 @@
   changes:
     - "Add `--scheduled-at` option to `toot post`, allows scheduling toots"
     - "Add `--description` option to `toot post`, for adding descriptions to media attachments (thanks @ansuz)"
+    - "Disable paging timeline when output is piped (thanks @stacyharper)"
 
 0.27.0:
   date: 2020-06-15

toot/commands.py

@@ -52,7 +52,7 @@ def timeline(app, user, args):
 
         print_timeline(items)
 
-        if args.once:
+        if args.once or not sys.stdout.isatty():
             break
 
         char = input("\nContinue? [Y/n] ")