Add powerful match subcommand to cmdline client

- Multiple output formats
- Signals matches via exit status for shell scripts
- Match against To, From, Subject via regular expressions
- Can optionally delete matched messages

cmd/client/main.go

@@ -6,6 +6,7 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"regexp"
 
 	"github.com/google/subcommands"
 )
@@ -13,6 +14,38 @@ import (
 var host = flag.String("host", "localhost", "host/IP of Inbucket server")
 var port = flag.Uint("port", 9000, "HTTP port of Inbucket server")
 
+// Allow subcommands to accept regular expressions as flags
+type regexFlag struct {
+	*regexp.Regexp
+}
+
+func (r *regexFlag) Defined() bool {
+	return r.Regexp != nil
+}
+
+func (r *regexFlag) Set(pattern string) error {
+	if pattern == "" {
+		r.Regexp = nil
+		return nil
+	}
+	re, err := regexp.Compile(pattern)
+	if err != nil {
+		return err
+	}
+	r.Regexp = re
+	return nil
+}
+
+func (r *regexFlag) String() string {
+	if r.Regexp == nil {
+		return ""
+	}
+	return r.Regexp.String()
+}
+
+// regexFlag must implement flag.Value
+var _ flag.Value = &regexFlag{}
+
 func main() {
 	// Important top-level flags
 	subcommands.ImportantFlag("host")
@@ -23,6 +56,7 @@ func main() {
 	subcommands.Register(subcommands.CommandsCommand(), "")
 	// Setup my commands
 	subcommands.Register(&listCmd{}, "")
+	subcommands.Register(&matchCmd{}, "")
 	subcommands.Register(&mboxCmd{}, "")
 	// Parse and execute
 	flag.Parse()