main: Add -version

Give callers an easy way to extract both the plugin version and the
dependency versions.  With this commit:

  $ ./terraform-provider-libvirt -version
  ./terraform-provider-libvirt 48adac3-dirty
  Compiled against library: libvirt 3.9.0
  Using library: libvirt 3.9.0
  Running hypervisor: QEMU 2.9.0
  Running against daemon: 3.9.0

The details are very similar to:

  $ virsh version --daemon
  Compiled against library: libvirt 3.9.0
  Using library: libvirt 3.9.0
  Using API: QEMU 3.9.0
  Running hypervisor: QEMU 2.9.0
  Running against daemon: 3.9.0

except the Go bindings do not currently expose the API version [1].
I've submitted a patch to libvirt-go adding ParseVersion there.  But
until then, carrying our own parseVersion shouldn't be too much
trouble.

I hunted around for a way to expose this in Terraform.  Currently:

  $ cat main.tf
  provider "libvirt" {
    uri = "qemu:///system"
  }
  trking@trking /tmp/test $ terraform version
  Terraform v0.11.8
  + provider.libvirt (unversioned)

but the RPC API is not particularly clear to me, and the versions
there may be extracted from plugin filenames and not from RPC calls.

[1]: https://libvirt.org/git/?p=libvirt-go.git;a=blob;f=connect.go;h=8cc7cc771f7d258400175df47fcc8b3779ef4930;hb=9c5bdce3c18faad94cb383e7ec42f5122a8c7fa1#l313

.github/ISSUE_TEMPLATE.md

@@ -5,15 +5,22 @@
 ``` openSUSE 42.2/ Centos7/ Ubuntu.. ```
 
 ### Terraform Version Report
-(Provided by running `terraform -v`.)
 
-### Libvirt version
+```sh
+terraform -v
+```
 
-```virsh --version```
+### Provider and libvirt versions
 
-### terraform-provider-libvirt plugin version (git-hash)
+```sh
+terraform-provider-libvirt -version
+```
 
-``` git log```
+If that gives you "was not built correctly", get the Git commit hash from your local provider repository:
+
+```sh
+git describe --always --abbrev=40 --dirty
+```
 ___
 # Description of Issue/Question
 

Makefile

@@ -1,7 +1,9 @@
+LDFLAGS += -X main.version=$$(git describe --always --abbrev=40 --dirty)
+
 default: build
 
 build: gofmtcheck golint vet
-	go build
+	go build -ldflags "${LDFLAGS}"
 
 install:
 	go install

main.go

@@ -1,20 +1,82 @@
 package main
 
 import (
-	"github.com/dmacvicar/terraform-provider-libvirt/libvirt"
-	"github.com/hashicorp/terraform/plugin"
+	"flag"
+	"fmt"
+	"log"
 	"math/rand"
+	"os"
 	"time"
+
+	"github.com/dmacvicar/terraform-provider-libvirt/libvirt"
+	"github.com/hashicorp/terraform/plugin"
+	libvirtgo "github.com/libvirt/libvirt-go"
 )
 
+var version = "was not built correctly" // set via the Makefile
+
 func main() {
+	versionFlag := flag.Bool("version", false, "print version information and exit")
+	flag.Parse()
+	if *versionFlag {
+		err := printVersion()
+		if err != nil {
+			log.Fatal(err)
+		}
+		os.Exit(0)
+	}
+
 	defer libvirt.CleanupLibvirtConnections()
 
 	plugin.Serve(&plugin.ServeOpts{
 		ProviderFunc: libvirt.Provider,
 	})
 }
 
+func printVersion() error {
+	fmt.Printf("%s %s\n", os.Args[0], version)
+
+	fmt.Printf("Compiled against library: libvirt %s\n", parseVersion(libvirtgo.VERSION_NUMBER))
+
+	libvirtVersion, err := libvirtgo.GetVersion()
+	if err != nil {
+		return err
+	}
+	fmt.Printf("Using library: libvirt %s\n", parseVersion(libvirtVersion))
+
+	conn, err := libvirtgo.NewConnect("qemu:///system")
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+
+	hvType, err := conn.GetType()
+	if err != nil {
+		return err
+	}
+	libvirtVersion, err = conn.GetVersion()
+	if err != nil {
+		return err
+	}
+	fmt.Printf("Running hypervisor: %s %s\n", hvType, parseVersion(libvirtVersion))
+
+	libvirtVersion, err = conn.GetLibVersion()
+	if err != nil {
+		return err
+	}
+	fmt.Printf("Running against daemon: %s\n", parseVersion(libvirtVersion))
+
+	return nil
+}
+
+func parseVersion(version uint32) string {
+	release := version % 1000
+	version /= 1000
+	minor := version % 1000
+	major := version / 1000
+	return fmt.Sprintf("%d.%d.%d", major, minor, release)
+}
+
 func init() {
 	rand.Seed(time.Now().UTC().UnixNano())
 }