build:add codecov.yml (pingcap#9618)

.codecov.yml

@@ -0,0 +1,45 @@
+codecov:
+  notify:
+    require_ci_to_pass: yes
+
+coverage:
+  precision: 4
+  round: down
+  range: "65...90"
+
+  status:
+    project: 
+      default:
+        threshold: 0.2 #Allow the coverage to drop by threshold%, and posting a success status.
+    patch: 
+      default:
+        target: 0% # trial operation
+    changes: no
+
+parsers:
+  gcov:
+    branch_detection:
+      conditional: yes
+      loop: yes
+      method: no
+      macro: no
+
+comment:
+  layout: "header, diff"
+  behavior: default
+  require_changes: no
+
+ignore:
+  - "LICENSES"
+  - "*_test.go"       
+  - ".git"
+  - "*.yml"
+  - "*.md"
+  - "cmd/.*"       
+  - "docs/.*"
+  - "vendor/.*"
+  - "ddl/failtest/.*"
+  - "ddl/testutil/.*"
+  - "executor/seqtest/.*"
+  - "metrics/.*"
+

Makefile

@@ -128,7 +128,8 @@ ifeq ("$(TRAVIS_COVERAGE)", "1")
 	@echo "Running in TRAVIS_COVERAGE mode."
 	@export log_level=error; \
 	$(GO) get github.com/go-playground/overalls
-	$(OVERALLS) -project=github.com/pingcap/tidb -covermode=count -ignore='.git,vendor,cmd,docs,LICENSES' -concurrency=1 || { $(GOFAIL_DISABLE); exit 1; }
+	$(OVERALLS) -project=github.com/pingcap/tidb -covermode=count -ignore='.git,vendor,cmd,docs,LICENSES,ddl/failtest,ddl/testutil/,executor/esqtest' \
+			-concurrency=1 || { $(GOFAIL_DISABLE); exit 1; }
 else
 	@echo "Running in native mode."
 	@export log_level=error; \