Swift Test: Add HTML coverage report

Currently, `swift test` supports generating a JSON coverage report,
which is great for ingesting into various systems. The JSON coverage
report generation is processed by `llvm-cov`` where SwiftPM is simply
orchestrating the command line invocation. The JSON, however, is not
very "human consumable friendly" while iterating at-desk.

This change adds an additional command line argument to swift test that
allows specify whether to generate a JSON or HTML report. Selecting HTML
will produce a `llvm-cov`` HTML report, that is more easily consumable
by a developer at desk. Similar to the JSON coverage report, Swift
Package Manager is only responsible for constructing the command line
argument that will be passed to `llvm-cov``, which will produce the HTML
report.

Since `llvm-cov show` (which would produce the HTML) has numerous CLI
arguments that allows configurations of the HTML report, this change
supports a response file for configuring the `llvm-cov show` command.
The response file is accessible from the Swift Package project.

Author: bkhouri

.swiftpm/configuration/coverage.html.report.args.txt

@@ -0,0 +1,12 @@
+--tab-size=10
+--coverage-watermark=80,20
+--enable-vtable-value-profiling
+--show-branch-summary
+--show-region-summary
+--show-branches=percent
+--show-mcdc-summary
+--show-expansions
+--show-instantiations
+--show-regions
+--show-directory-coverage
+--show-line-counts

Package.swift

@@ -1108,7 +1108,7 @@ if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
         // utils/update_checkout/update-checkout-config.json
         // They are used to build the official swift toolchain.
         .package(url: "https://github.com/swiftlang/swift-syntax.git", branch: relatedDependenciesBranch),
-        .package(url: "https://github.com/apple/swift-argument-parser.git", revision: "1.5.1"),
+        .package(url: "https://github.com/apple/swift-argument-parser.git", revision: "1.6.1"),
         .package(url: "https://github.com/apple/swift-crypto.git", revision: "3.12.5"),
         .package(url: "https://github.com/apple/swift-system.git", revision: "1.5.0"),
         .package(url: "https://github.com/apple/swift-collections.git", revision: "1.1.6"),

Sources/Commands/SwiftBuildCommand.swift

@@ -76,9 +76,15 @@ struct BuildCommandOptions: ParsableArguments {
     var buildTests: Bool = false
 
     /// Whether to enable code coverage.
-    @Flag(name: .customLong("code-coverage"),
-          inversion: .prefixedEnableDisable,
-          help: "Enable code coverage.")
+    @Flag(
+        name: [
+            .customLong("codecov"),
+            .customLong("code-coverage"),
+            .customLong("coverage"),
+        ],
+        inversion: .prefixedEnableDisable,
+        help: "Enable code coverage.",
+    )
     var enableCodeCoverage: Bool = false
 
     /// If the binary output path should be printed.