Added version option

.gitignore

@@ -1 +1,2 @@
 /output/
+VERSION

Makefile

@@ -1,5 +1,7 @@
 NAME=kubectl-tmux-exec
-VERSION=0.1.0
+GIT_TAG := $(shell git describe --tags --abbrev=0)
+GIT_COMMIT_ID := $(shell git rev-parse HEAD)
+VERSION := $(GIT_TAG:v%=%)
 
 OUTPUT_DIR=output
 RELEASE_FILE_NAME=$(NAME)-$(VERSION).tar.gz
@@ -8,19 +10,22 @@ SIG_FILE_NAME=$(NAME)-$(VERSION).asc
 SIG_FILE_PATH=$(OUTPUT_DIR)/$(SIG_FILE_NAME)
 CHECKSUM_FILE_NAME=$(RELEASE_FILE_NAME).sha256
 CHECKSUM_FILE_PATH=$(OUTPUT_DIR)/$(CHECKSUM_FILE_NAME)
+VERSION_FILE_PATH=VERSION
 
 ifeq ($(OS), Windows_NT)
     OS_UNAME := Windows
 else
     OS_UNAME := $(shell uname -s)
 endif
 
-.PHONY: build sign checksum clean mk-output-dir test
+.PHONY: build version sign checksum clean mk-output-dir test
 
 all: test $(RELEASE_FILE_PATH) $(CHECKSUM_FILE_PATH)
 
 build: $(RELEASE_FILE_PATH)
 
+version: $(VERSION_FILE_PATH)
+
 test:
 	bats test/
 
@@ -32,10 +37,13 @@ mk-output-dir:
 	mkdir -p $(OUTPUT_DIR)
 
 clean:
-	rm -rf $(RELEASE_FILE_PATH) $(CHECKSUM_FILE_PATH) $(SIG_FILE_PATH)
+	rm -rf $(VERSION_FILE_PATH) $(RELEASE_FILE_PATH) $(CHECKSUM_FILE_PATH) $(SIG_FILE_PATH)
+
+$(VERSION_FILE_PATH):
+	echo "$(VERSION) (commit = $(GIT_COMMIT_ID))" > $(VERSION_FILE_PATH)
 
-$(RELEASE_FILE_PATH): mk-output-dir
-	tar czvf $(RELEASE_FILE_PATH) bin/ LICENSE
+$(RELEASE_FILE_PATH): mk-output-dir $(VERSION_FILE_PATH)
+	tar czvf $(RELEASE_FILE_PATH) bin/ LICENSE $(VERSION_FILE_PATH)
 
 $(SIG_FILE_PATH): $(RELEASE_FILE_PATH)
 	gpg -ab $(RELEASE_FILE_PATH)

bin/kubectl-tmux_exec

@@ -21,6 +21,15 @@
 
 set -euf -o pipefail
 
+# Stack Overflow: https://stackoverflow.com/a/246128/1122665
+SOURCE="${BASH_SOURCE[0]}"
+while [[ -h "$SOURCE" ]]; do
+  PROG_DIR="$( cd -P "$( dirname "$SOURCE" )" >/dev/null 2>&1 && pwd )"
+  SOURCE="$(readlink "$SOURCE")"
+  [[ $SOURCE != /* ]] && SOURCE="$PROG_DIR/$SOURCE"
+done
+PROG_DIR="$( cd -P "$( dirname "$SOURCE" )" >/dev/null 2>&1 && pwd )"
+
 readonly PROG_NAME='kubectl tmux-exec'
 
 declare -ra KUBECTL_SHORT_OPTS=(
@@ -71,6 +80,7 @@ Examples:
   ${PROG_NAME} -f - /bin/bash # read from stdin
 
 Options:
+  -V, --version: Print the version information
   -c, --container='': Container name. If omitted, the first container in the pod will be chosen
   -i, --stdin=true: Pass stdin to the container (deprecated, since it's enabled by default)
   -t, --tty=true: Stdin is a TTY (deprecated, since it's enabled by default)
@@ -88,6 +98,15 @@ Use "kubectl options" for a list of global command-line options (applies to all
 EOF
 }
 
+function print_version() {
+    local version_file="${PROG_DIR}/../VERSION"
+    if [[ -f "${version_file}" ]]; then
+        cat "${version_file}"
+    else
+        echo "unknown"
+    fi
+}
+
 function check_required_executables() {
     for exe in "$@"; do
         if ! which "${exe}" 2>&1 >/dev/null; then
@@ -137,8 +156,8 @@ function array_contains() {
 
 function main() {
     local opts
-    opts=$(ggetopt -o hitdc:l:f:"$(printf '%s:' "${KUBECTL_SHORT_OPTS[@]}")" --long \
-        help,stdin,tty,detach,container:,selector:,remain-on-exit,select-layout:,file:,"$(printf '%s:,' "${KUBECTL_LONG_OPTS[@]}")","$(printf '%s,' "${KUBECTL_NOARG_LONG_OPTS[@]}")" -- "$@")
+    opts=$(ggetopt -o hVitdc:l:f:"$(printf '%s:' "${KUBECTL_SHORT_OPTS[@]}")" --long \
+        help,version,stdin,tty,detach,container:,selector:,remain-on-exit,select-layout:,file:,"$(printf '%s:,' "${KUBECTL_LONG_OPTS[@]}")","$(printf '%s,' "${KUBECTL_NOARG_LONG_OPTS[@]}")" -- "$@")
     eval set -- $opts
 
     local selector
@@ -155,6 +174,10 @@ function main() {
                 usage
                 exit 0
                 ;;
+            -V|--version)
+                print_version
+                exit 0
+                ;;
             -c|--container)
                 shift
                 container_name="$1"