Add package (pkg) resource

This is based on PackageKit, which means events, *and* we automatically
get support for any of the backends that PackageKit supports. This means
dpkg, and rpm are both first class citizens! Many other backends will
surely work, although thorough testing is left as an exercise to the
reader, or to someone who would like to write more test cases!

Unfortunately at the moment, there are a few upstream PackageKit bugs
which cause us issues, but those have been apparently resolved upstream.
If you experience issues with an old version of PackageKit, test if it
is working correctly before blaming mgmt :)

In parallel, mgmt might increase the testing surface for PackageKit, so
hopefully this makes it more robust for everyone involved!

Lastly, I'd like to point out that many great things that are typically
used for servers do start in the GNOME desktop world. Help support your
GNOME GNU/Linux desktop today!

config.go

@@ -45,6 +45,7 @@ type GraphConfig struct {
 	Graph     string `yaml:"graph"`
 	Resources struct {
 		Noop []NoopRes `yaml:"noop"`
+		Pkg  []PkgRes  `yaml:"pkg"`
 		File []FileRes `yaml:"file"`
 		Svc  []SvcRes  `yaml:"svc"`
 		Exec []ExecRes `yaml:"exec"`
@@ -94,12 +95,14 @@ func ParseConfigFromFile(filename string) *GraphConfig {
 func UpdateGraphFromConfig(config *GraphConfig, hostname string, g *Graph, etcdO *EtcdWObject) bool {
 
 	var NoopMap = make(map[string]*Vertex)
+	var PkgMap = make(map[string]*Vertex)
 	var FileMap = make(map[string]*Vertex)
 	var SvcMap = make(map[string]*Vertex)
 	var ExecMap = make(map[string]*Vertex)
 
 	var lookup = make(map[string]map[string]*Vertex)
 	lookup["noop"] = NoopMap
+	lookup["pkg"] = PkgMap
 	lookup["file"] = FileMap
 	lookup["svc"] = SvcMap
 	lookup["exec"] = ExecMap
@@ -121,6 +124,17 @@ func UpdateGraphFromConfig(config *GraphConfig, hostname string, g *Graph, etcdO
 		keep = append(keep, v) // append
 	}
 
+	for _, t := range config.Resources.Pkg {
+		obj := NewPkgRes(t.Name, t.State, false, false, false)
+		v := g.GetVertexMatch(obj)
+		if v == nil { // no match found
+			v = NewVertex(obj)
+			g.AddVertex(v) // call standalone in case not part of an edge
+		}
+		PkgMap[obj.Name] = v   // used for constructing edges
+		keep = append(keep, v) // append
+	}
+
 	for _, t := range config.Resources.File {
 		// XXX: should we export based on a @@ prefix, or a metaparam
 		// like exported => true || exported => (host pattern)||(other pattern?)

examples/pkg1.yaml

@@ -0,0 +1,7 @@
+---
+graph: mygraph
+resources:
+  pkg:
+  - name: powertop
+    state: installed
+edges: []

examples/pkg2.yaml

@@ -0,0 +1,7 @@
+---
+graph: mygraph
+resources:
+  pkg:
+  - name: powertop
+    state: uninstalled
+edges: []

misc.go

@@ -21,6 +21,7 @@ import (
 	"bytes"
 	"encoding/base64"
 	"encoding/gob"
+	"github.com/godbus/dbus"
 	"path"
 	"strings"
 	"time"
@@ -120,3 +121,22 @@ func TimeAfterOrBlock(t int) <-chan time.Time {
 	}
 	return time.After(time.Duration(t) * time.Second)
 }
+
+// making using the private bus usable, should be upstream:
+// TODO: https://github.com/godbus/dbus/issues/15
+func SystemBusPrivateUsable() (conn *dbus.Conn, err error) {
+	conn, err = dbus.SystemBusPrivate()
+	if err != nil {
+		return nil, err
+	}
+	if err = conn.Auth(nil); err != nil {
+		conn.Close()
+		conn = nil
+		return
+	}
+	if err = conn.Hello(); err != nil {
+		conn.Close()
+		conn = nil
+	}
+	return conn, nil // success
+}