ci: switch to codecov cli on appveyor

This change replaces the legacy codecov uploader on macos with a
specific codecov-cli (the uploader's modern replacement) version that is known
to support several CPUs.
Fixes datalad#756

.appveyor.yml

@@ -53,7 +53,7 @@ build: off
 
 environment:
   # unless indicated otherwise, we test datalad_next
-  DTS: datalad_next
+  DTS: datalad_next.commands
   # SSH testing is done via a side-loaded container that provides a POSIX/SSHable
   # server environment
   DATALAD_TESTS_DOCKER_SSHD_SECKEY_DOWNLOADURL: https://ci.appveyor.com/api/projects/mih/datalad-ci-docker-containers/artifacts/recipes/sshd/id_rsa?job=sshd
@@ -118,7 +118,7 @@ environment:
       PY: 3.8
       INSTALL_GITANNEX: git-annex
       DATALAD_LOCATIONS_SOCKETS: /Users/appveyor/DLTMP/sockets
-      CODECOV_BINARY: https://uploader.codecov.io/latest/macos/codecov
+      CODECOV_BINARY: https://cli.codecov.io/v0.7.4/macos/codecov
       DATALAD_TESTS_SSH: 1
       # no docker on Mac, we log into self
       # 'test_publish_target_url' relies git-annex being installed on the
@@ -333,7 +333,8 @@ for:
       - python -m coverage xml
       - "curl -Os $CODECOV_BINARY"
       - chmod +x codecov
-      - ./codecov
+      # the do-upload subcommand seems to work for the codecov-cli and legacy uploader
+      - ./codecov do-upload
 
     on_finish:
       # conditionally block the exit of a CI run for direct debugging