feat(proc-cmdline): Parse /proc/cmdline for cloud-config-url

If the --from-proc-cmdline flag is given to coreos-cloudinit, the local
/proc/cmdline file will be parsed for a cloud-config-url

datasource/proc_cmdline_test.go

@@ -0,0 +1,47 @@
+package datasource
+
+import (
+	"testing"
+)
+
+func TestParseCmdlineCloudConfigFound(t *testing.T) {
+	tests := []struct {
+		input  string
+		expect string
+	}{
+		{
+			"cloud-config-url=example.com",
+			"example.com",
+		},
+		{
+			"cloud_config_url=example.com",
+			"example.com",
+		},
+		{
+			"cloud-config-url cloud-config-url=example.com",
+			"example.com",
+		},
+		{
+			"cloud-config-url= cloud-config-url=example.com",
+			"example.com",
+		},
+		{
+			"cloud-config-url=one.example.com cloud-config-url=two.example.com",
+			"two.example.com",
+		},
+		{
+			"foo=bar cloud-config-url=example.com ping=pong",
+			"example.com",
+		},
+	}
+
+	for i, tt := range tests {
+		output, err := findCloudConfigURL(tt.input)
+		if output != tt.expect {
+			t.Errorf("Test case %d failed: %s != %s", i, output, tt.expect)
+		}
+		if err != nil {
+			t.Errorf("Test case %d produced error: %v", i, err)
+		}
+	}
+}