version: Add a version command

And adjust 'runc --version' to print exactly the same content.

The:

  $ COMMAND --version

interface is a popular one for this information and makes a lot of
sense for single-action commands.  For example, printf(1) [1] is only
ever going to do one meaningful thing, so --version, --help, and other
command-like actions work well as options.

Umbrella commands with multiple sub-commands, on the other hand, have
a more consistent interface if '... and exit' actions get their own
sub-commands.  That allows you to declare an interface like:

  $ COMMAND [global-options] SUB-COMMAND [sub-command-specific-options] [sub-command-specific-arguments]

without having to say "except if you use a sub-command-like global
option, in which case SUB-COMMAND is not allowed".

With this commit, we add support for 'version' while keeping
--version, because while 'version' makes more sense for umbrella
commands, a user may not know if runc is an umbrella command when they
ask for the version.

Existing umbrella commands are not particularly consistent:

* git(1) supports both --version and 'version', --help and 'help'.
* btrfs(8) supports both --version and 'version', --help and 'help'.
* ip(1) supports -V / -Version and 'help'.
* npm supports 'version' and 'help'.
* pip supports '--version', --help and 'help'.

Setting .Version to the empty string takes advantage of the {{if
.Version}} conditional [2] to avoid --help showing:

  VERSION:
     0.0.0

because we are no longer setting .Version.  I floated a few options
[4], and Mike Brown (the only one with a preference) was in favor of
dropping the VERSION section [5] (which turned out to not need a
AppHelpTemplate adjustment ;).

The help tests ensure that attempting to remove "VERSION" from the
help output does not change the output (i.e. that the output didn't
contain "VERSION" to begin with).  That protects us from subsequent
urfave/cli changes breaking the empty-string .Version approach.

[1]: http://www.man7.org/linux/man-pages/man1/printf.1.html
[2]: /~https://github.com/urfave/cli/blob/v1.18.1/README.md#customization-1
[3]: #940 (comment)
[4]: #940 (comment)
[5]: #940 (comment)

Signed-off-by: W. Trevor King <wking@tremily.us>

main.go

@@ -3,21 +3,11 @@ package main
 import (
 	"fmt"
 	"os"
-	"strings"
 
 	"github.com/Sirupsen/logrus"
-	"github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/urfave/cli"
 )
 
-// version will be populated by the Makefile, read from
-// VERSION file of the source code.
-var version = ""
-
-// gitCommit will be the hash that the binary was built from
-// and will be populated by the Makefile
-var gitCommit = ""
-
 const (
 	specConfig = "config.json"
 	usage      = `Open Container Initiative runtime
@@ -49,16 +39,11 @@ func main() {
 	app := cli.NewApp()
 	app.Name = "runc"
 	app.Usage = usage
+	app.Version = ""
 
-	var v []string
-	if version != "" {
-		v = append(v, version)
-	}
-	if gitCommit != "" {
-		v = append(v, fmt.Sprintf("commit: %s", gitCommit))
+	cli.VersionPrinter = func(context *cli.Context) {
+		printVersion(context)
 	}
-	v = append(v, fmt.Sprintf("spec: %s", specs.Version))
-	app.Version = strings.Join(v, "\n")
 	app.Flags = []cli.Flag{
 		cli.BoolFlag{
 			Name:  "debug",
@@ -107,6 +92,7 @@ func main() {
 		startCommand,
 		stateCommand,
 		updateCommand,
+		versionCommand,
 	}
 	app.Before = func(context *cli.Context) error {
 		if context.GlobalBool("debug") {

tests/integration/help.bats

@@ -7,11 +7,13 @@ load helpers
   [ "$status" -eq 0 ]
   [[ ${lines[0]} =~ NAME:+ ]]
   [[ ${lines[1]} =~ runc\ '-'\ Open\ Container\ Initiative\ runtime+ ]]
+  [ "${output}" = "${output/VERSION/}" ]
 
   runc --help
   [ "$status" -eq 0 ]
   [[ ${lines[0]} =~ NAME:+ ]]
   [[ ${lines[1]} =~ runc\ '-'\ Open\ Container\ Initiative\ runtime+ ]]
+  [ "${output}" = "${output/VERSION/}" ]
 }
 
 @test "runc command -h" {

tests/integration/version.bats

@@ -2,10 +2,18 @@
 
 load helpers
 
-@test "runc version" {
+@test "runc --version" {
   runc -v
   [ "$status" -eq 0 ]
-  [[ ${lines[0]} =~ runc\ version\ [0-9]+\.[0-9]+\.[0-9]+ ]]
+  [[ ${lines[0]} =~ runC\ [0-9]+\.[0-9]+\.[0-9]+ ]]
+  [[ ${lines[1]} =~ commit:+ ]]
+  [[ ${lines[2]} =~ spec:\ [0-9]+\.[0-9]+\.[0-9]+ ]]
+}
+
+@test "runc version" {
+  runc version
+  [ "$status" -eq 0 ]
+  [[ ${lines[0]} =~ runC\ [0-9]+\.[0-9]+\.[0-9]+ ]]
   [[ ${lines[1]} =~ commit:+ ]]
   [[ ${lines[2]} =~ spec:\ [0-9]+\.[0-9]+\.[0-9]+ ]]
 }

version.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/urfave/cli"
+)
+
+// version will be populated by the Makefile, read from
+// VERSION file of the source code.
+var version = ""
+
+// gitCommit will be the hash that the binary was built from
+// and will be populated by the Makefile
+var gitCommit = ""
+
+var versionCommand = cli.Command{
+	Name:        "version",
+	Usage:       "output the runtime version",
+	Description: `The version command outputs the runtime version.`,
+	Action:      printVersion,
+}
+
+func printVersion(context *cli.Context) (err error) {
+	if version == "" {
+		_, err = os.Stdout.WriteString("runC unknown\n")
+	} else {
+		_, err = os.Stdout.WriteString(fmt.Sprintf("runC %s\n", version))
+	}
+	if err != nil {
+		return err
+	}
+	if gitCommit != "" {
+		_, err = os.Stdout.WriteString(fmt.Sprintf("commit: %s\n", gitCommit))
+		if err != nil {
+			return err
+		}
+	}
+	_, err = os.Stdout.WriteString(fmt.Sprintf("spec: %s\n", specs.Version))
+	return err
+}