Allow filtering repos by topic

Signed-off-by: Knut Ahlers <knut@ahlers.me>

main.go

@@ -29,6 +29,7 @@ var (
 		NameRegex      string   `flag:"name-regex" default:".*" description:"Regex to match the name against"`
 		Output         string   `flag:"out,o" default:"-" description:"File to write to (- = stdout)"`
 		Template       string   `flag:"template" default:"" description:"Template file to use for rendering" validate:"nonzero"`
+		TopicFilter    []string `flag:"topic,t" default:"" description:"Filter by topic (Format: 'topic' to include, '-topic' to exclude)"`
 		VersionAndExit bool     `flag:"version" default:"false" description:"Prints current version and exits"`
 	}{}
 
@@ -77,6 +78,10 @@ func main() {
 			continue
 		}
 
+		if !matchTopicFilter(repo) {
+			continue
+		}
+
 		skip := false
 
 		for _, f := range cfg.Filters {
@@ -165,6 +170,25 @@ func fetchRepos() ([]*github.Repository, error) {
 	return repos, nil
 }
 
+func matchTopicFilter(repo *github.Repository) bool {
+	for _, topic := range cfg.TopicFilter {
+		if topic == "" {
+			continue
+		}
+
+		negate := topic[0] == '-'
+		if negate {
+			topic = topic[1:len(topic)]
+		}
+
+		if str.StringInSlice(topic, repo.Topics) != negate {
+			return true
+		}
+	}
+
+	return false
+}
+
 func render(repo *github.Repository) error {
 	var outFile io.Writer
 	if cfg.Output == "-" {