Add codecov for automated code coverage (redis#13393)

This PR introduces Codecov to automate code coverage tracking for our
project's tests.
For more information about the Codecov platform, please refer to
https://docs.codecov.com/docs/quick-start

---------

Co-authored-by: debing.sun <[email protected]>

Author: vitahlin

.github/workflows/codecov.yml

@@ -0,0 +1,24 @@
+name: "Codecov"
+
+# Enabling on each push is to display the coverage changes in every PR, 
+# where each PR needs to be compared against the coverage of the head commit
+on: [push, pull_request]
+
+jobs:
+  code-coverage:
+    runs-on: ubuntu-22.04
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v4
+
+    - name: Install lcov and run test
+      run: |
+        sudo apt-get install lcov
+        make lcov
+
+    - name: Upload coverage reports to Codecov
+      uses: codecov/codecov-action@v4
+      with:
+        token: ${{ secrets.CODECOV_TOKEN }}
+        file: ./src/redis.info

README.md

@@ -1,3 +1,5 @@
+[![codecov](https://codecov.io/github/redis/redis/graph/badge.svg?token=6bVHb5fRuz)](https://codecov.io/github/redis/redis)
+
 This README is just a fast *quick start* document. You can find more detailed documentation at [redis.io](https://redis.io).
 
 What is Redis?

codecov.yml

@@ -0,0 +1,19 @@
+coverage:
+  status:
+    patch:
+      default:
+        informational: true
+    project:
+      default:
+        informational: true
+
+comment:
+  require_changes: false
+  require_head: false
+  require_base: false
+  layout: "condensed_header, diff, files"
+  hide_project_coverage: false
+  behavior: default
+
+github_checks:
+  annotations: false

src/Makefile

@@ -487,8 +487,9 @@ test-cluster: $(REDIS_SERVER_NAME) $(REDIS_CLI_NAME)
 check: test
 
 lcov:
+	@lcov --version
 	$(MAKE) gcov
-	@(set -e; cd ..; ./runtest --clients 1)
+	@(set -e; cd ..; ./runtest)
 	@geninfo -o redis.info .
 	@genhtml --legend -o lcov-html redis.info