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

scripts/build-rpm.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 #
 # Package the (already built) chlog binary into an RPM with nfpm, bundling
-# chcat/chtail/chgrep symlinks and generated bash/zsh/fish shell completions.
+# generated bash/zsh/fish shell completions.
 # Usage: scripts/build-rpm.sh [version]   (version defaults to $CI_COMMIT_TAG)
 #
 set -euo pipefail
@@ -12,7 +12,6 @@ cd "${ROOT_DIR}"
 VERSION="${1:-${CI_COMMIT_TAG:-0.0.0-dev}}"
 VERSION="${VERSION#v}" # strip a leading v
 BINARY="chlog"
-NAMES=(chlog chcat chtail chgrep)
 DIST="dist"
 
 if [ ! -f "${DIST}/${BINARY}" ]; then
@@ -20,26 +19,19 @@ if [ ! -f "${DIST}/${BINARY}" ]; then
   exit 1
 fi
 
-for l in chcat chtail chgrep; do
-  ln -sf "${BINARY}" "${DIST}/${l}"
-done
-
-# Generate shell completions per entrypoint name so they always match the
-# shipped flags/subcommands (each name dispatches to its own command tree).
+# Generate shell completions so they always match the shipped flags/subcommands.
 COMP_DIR="${DIST}/completions"
 mkdir -p "${COMP_DIR}"
-for b in "${NAMES[@]}"; do
-  "./${DIST}/${b}" completion bash >"${COMP_DIR}/${b}.bash"
-  "./${DIST}/${b}" completion zsh >"${COMP_DIR}/_${b}"
-  "./${DIST}/${b}" completion fish >"${COMP_DIR}/${b}.fish"
-done
+"./${DIST}/${BINARY}" completion bash >"${COMP_DIR}/${BINARY}.bash"
+"./${DIST}/${BINARY}" completion zsh >"${COMP_DIR}/_${BINARY}"
+"./${DIST}/${BINARY}" completion fish >"${COMP_DIR}/${BINARY}.fish"
 
 export PACKAGE_NAME="clickhouse-tools"
 export PACKAGE_VERSION="${VERSION}"
 export PACKAGE_RELEASE="1"
 export PACKAGE_ARCH="amd64"
 export PACKAGE_PLATFORM="linux"
-export PACKAGE_DESCRIPTION="CLI tools for the ClickHouse log store: chlog with chcat (print), chtail (follow) and chgrep (search) entrypoints"
+export PACKAGE_DESCRIPTION="CLI tools for the ClickHouse log store: chlog with cat (print), tail (follow) and grep (search) subcommands"
 export PACKAGE_MAINTAINER="Ben Vincent <ben@unkin.net>"
 export PACKAGE_HOMEPAGE="https://git.unkin.net/unkin/clickhouse-tools"
 export PACKAGE_LICENSE="MIT"