Add codecov.yml

MANIFEST.SKIP

@@ -45,6 +45,7 @@ src/Makefile$
 src/Makefile_obj$
 include/verilated.mk$
 test_regress/.gdbinit$
+codecov.yml
 config.cache$
 config.status$
 verilator\.log

codecov.yml

@@ -0,0 +1,38 @@
+# DESCRIPTION: codecov.io config
+#
+# Copyright 2020-2020 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+####################
+# Validate:
+#  curl --data-binary @codecov.yml https://codecov.io/validate
+
+codecov:
+  require_ci_to_pass: no
+
+coverage:
+  precision: 2
+  round: down
+  range: "70...100"
+  ignore:
+    - "ci"
+    - "docs"
+    - "examples"
+    - "include/gtkwave"
+    - "include/vltstd"
+    - "test_regress"
+
+parsers:
+  gcov:
+    branch_detection:
+      conditional: yes
+      loop: yes
+      method: no
+      macro: no
+
+comment:
+  layout: "reach,diff,flags,tree"
+  behavior: default
+  require_changes: yes