Build detailed coverage HTML pages (#649)

Change coverage-report.sh to produce an HTML archive with full coverage
information (with all source files and per-line coverage information).
Let the HTML archive be uploaded by Continuous Integration as one of
artifacts.

.github/workflows/makefile.yml

@@ -106,6 +106,12 @@ jobs:
           scripts/parse-coverage-output.py < coverage-output.txt
         )"
 
+    - name: Upload coverage report
+      uses: actions/upload-artifact@v3
+      with:
+        name: coverage-report-detailed.zip
+        path: coverage-report-detailed/
+
   # Post an autogenerated comment on the Pull Request (in case the action is run
   # because of one).
   post-results-comment:

.gitignore

@@ -1,2 +1,3 @@
 /binaries-for-github-release/
 /built_app_packages/
+/coverage-report-detailed/

coverage-report.sh

@@ -71,6 +71,13 @@ done
 # weirdness of llvm-cov's CLI). Trim the leading whitespace via one sed
 # invocation and replace inner spaces with the flag using the second one.
 llvm_cov_args=$(echo "${executables}" | sed 's/^ //g' | sed 's/ / -object /g')
+# Create detailed coverage HTML page with per-line information.
+llvm-cov show \
+  -format=html \
+  ${llvm_cov_args} \
+  -instr-profile=env/coverage-artifacts/all.profdata \
+  -ignore-filename-regex=${IGNORE_FILENAME_REGEX} \
+  -output-dir=coverage-report-detailed/
 # Print the coverage report table to stdout, so that the report can be parsed by
 # the next steps of the pipeline. (Everything above was logged to stderr.)
 llvm-cov report \