Drop chcat/chtail/chgrep symlink entrypoints; ship chlog subcommands only

The RPM's /usr/bin/chcat conflicts with SELinux's
policycoreutils-python-utils on Fedora. Per Ben: remove the symlink
entrypoints entirely and ship only the chlog binary with cat/tail/grep
subcommands.

- Remove chcat/chtail/chgrep symlinks and their completions from
  nfpm.yaml, build-rpm.sh and the Makefile
- Remove the argv[0] dispatch in main.go; subcommands are unchanged
- Update the completion test to cover chlog only
- Update README usage to chlog cat|tail|grep

main.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"os"
 	"os/signal"
-	"path/filepath"
 	"strings"
 	"syscall"
 	"time"
@@ -88,10 +87,10 @@ func (cf *commonFlags) formatter() (chlog.Formatter, error) {
 	return chlog.NewFormatter(cf.format, color)
 }
 
-func newCatCmd(use string) *cobra.Command {
+func newCatCmd() *cobra.Command {
 	cf := &commonFlags{}
 	cmd := &cobra.Command{
-		Use:   use,
+		Use:   "cat",
 		Short: "Print logs from the ClickHouse log store, oldest first",
 		Args:  cobra.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -114,10 +113,10 @@ func newCatCmd(use string) *cobra.Command {
 	return cmd
 }
 
-func newTailCmd(use string) *cobra.Command {
+func newTailCmd() *cobra.Command {
 	cf := &commonFlags{}
 	cmd := &cobra.Command{
-		Use:   use,
+		Use:   "tail",
 		Short: "Follow logs from the ClickHouse log store",
 		Args:  cobra.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -146,7 +145,7 @@ func newTailCmd(use string) *cobra.Command {
 	return cmd
 }
 
-func newGrepCmd(use string) *cobra.Command {
+func newGrepCmd() *cobra.Command {
 	cf := &commonFlags{}
 	var (
 		regex      bool
@@ -155,7 +154,7 @@ func newGrepCmd(use string) *cobra.Command {
 		force      bool
 	)
 	cmd := &cobra.Command{
-		Use:   use + " <pattern>",
+		Use:   "grep <pattern>",
 		Short: "Search log messages in the ClickHouse log store",
 		Args:  cobra.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -217,32 +216,14 @@ func newRootCmd() *cobra.Command {
 		SilenceUsage:  true,
 		SilenceErrors: true,
 	}
-	root.AddCommand(newCatCmd("cat"), newTailCmd("tail"), newGrepCmd("grep"))
+	root.AddCommand(newCatCmd(), newTailCmd(), newGrepCmd())
 	return root
 }
 
-func entrypoint() *cobra.Command {
-	var cmd *cobra.Command
-	switch filepath.Base(os.Args[0]) {
-	case "chcat":
-		cmd = newCatCmd("chcat")
-	case "chtail":
-		cmd = newTailCmd("chtail")
-	case "chgrep":
-		cmd = newGrepCmd("chgrep")
-	default:
-		return newRootCmd()
-	}
-	cmd.Version = version
-	cmd.SilenceUsage = true
-	cmd.SilenceErrors = true
-	return cmd
-}
-
 func main() {
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
-	if err := entrypoint().ExecuteContext(ctx); err != nil {
+	if err := newRootCmd().ExecuteContext(ctx); err != nil {
 		fmt.Fprintln(os.Stderr, "error:", err)
 		os.Exit(1)
 	}