pkg/cover: allow paths to be excluded from stats

Some sub paths may not be covered due to hardware configuration, or lack
of interest. This patch allows them to be excluded from the stats. This
can be convenient if the excluded paths are deep in the hierarchy:

{
    "name": "sound",
    "path": [
	"techpack/audio",
	"-techpack/audio/asoc/aaa/bbb"
	"-techpack/audio/asoc/aaa/ccc"
    ]
}

Author: quic-likaid

pkg/cover/html.go

@@ -445,8 +445,12 @@ func groupCoverByFilePrefixes(datas []fileStats, subsystems []mgrconfig.Subsyste
 		var percentCoveredFunc float64
 
 		for _, path := range subsystem.Paths {
+			if strings.HasPrefix(path, "-") {
+				continue
+			}
+			excludes := buildExcludePaths(path, subsystem.Paths)
 			for _, data := range datas {
-				if !strings.HasPrefix(data.Name, path) {
+				if !strings.HasPrefix(data.Name, path) || isExcluded(data.Name, excludes) {
 					continue
 				}
 				coveredLines += data.CoveredLines
@@ -490,6 +494,25 @@ func groupCoverByFilePrefixes(datas []fileStats, subsystems []mgrconfig.Subsyste
 	return d
 }
 
+func buildExcludePaths(prefix string, paths []string) []string {
+	var excludes []string
+	for _, path := range paths {
+		if strings.HasPrefix(path, "-") && strings.HasPrefix(path[1:], prefix) {
+			excludes = append(excludes, path[1:])
+		}
+	}
+	return excludes
+}
+
+func isExcluded(path string, excludes []string) bool {
+	for _, exclude := range excludes {
+		if strings.HasPrefix(path, exclude) {
+			return true
+		}
+	}
+	return false
+}
+
 func (rg *ReportGenerator) DoSubsystemCover(w io.Writer, params HandlerParams) error {
 	var progs = fixUpPCs(params.Progs, params.Filter)
 	data, err := rg.convertToStats(progs)

pkg/mgrconfig/config.go

@@ -51,9 +51,9 @@ type Config struct {
 	KernelBuildSrc string `json:"kernel_build_src,omitempty"`
 	// Is the kernel built separately from the modules? (Specific to Android builds)
 	AndroidSplitBuild bool `json:"android_split_build"`
-	// Kernel subsystem with paths to each subsystem
+	// Kernel subsystem with paths to each subsystem, paths starting with "-" will be excluded
 	//	"kernel_subsystem": [
-	//		{ "name": "sound", "path": ["sound", "techpack/audio"]},
+	//		{ "name": "sound", "path": ["sound", "techpack/audio", "-techpack/audio/dsp"]},
 	//		{ "name": "mydriver": "path": ["mydriver_path"]}
 	//	]
 	KernelSubsystem []Subsystem `json:"kernel_subsystem,omitempty"`