Milo: Extract the rietveld information from buildbot.

appengine/cmd/milo/buildbot/build.go

Index: appengine/cmd/milo/buildbot/build.go
diff --git a/appengine/cmd/milo/buildbot/build.go b/appengine/cmd/milo/buildbot/build.go
index 772075574d632ba24656e48420e8d9507de46da7..2404c1f50bfd698530a71e9d7c0a7c88c0ea598e 100644
--- a/appengine/cmd/milo/buildbot/build.go
+++ b/appengine/cmd/milo/buildbot/build.go
@@ -341,6 +341,38 @@ func blame(b *buildbotBuild) (result []*resp.Commit) {
 	return
 }
 
+// sourcestamp extracts the source stamp from various parts of a buildbot build,
+// including the properties.
+func sourcestamp(b *buildbotBuild) *resp.SourceStamp {
+	ss := &resp.SourceStamp{}
+	rietveld := ""
+	issue := int64(-1)
+	// TODO(hinoka): Gerrit URLs.
+	for _, prop := range b.Properties {
+		key := prop[0].(string)
+		value := prop[1]
+		switch key {
+		case "rietveld":
+			rietveld = value.(string)
+		case "issue":
+			issue = int64(value.(float64))
+		case "got_revision":
+			ss.Revision = value.(string)
+		}
+	}

[nodir, 2016/06/28 02:06:44]

This code will panic if user input malformed, we should not panic if user gave
us bad data. Please add checks in type assertions and log erros if type
assertions fail

[Ryan Tseng, 2016/06/28 21:49:31]

Done.

+	if issue != -1 && rietveld == "" {
+		// Default rietveld server
+		rietveld = "https://codereview.chromium.org"

[nodir, 2016/06/28 02:06:44]

Do we have to define defaults in our code? Do we have builds that do not specify
rietveld hostname?

[Ryan Tseng, 2016/06/28 21:49:31]

Not sure, this is just incase.  I'll remove this

+	}
+	if issue != -1 {
+		ss.Changelist = &resp.Link{
+			Label: fmt.Sprintf("Issue %d", issue),
+			URL:   fmt.Sprintf("%s/%d", rietveld, issue),

[nodir, 2016/06/28 02:06:44]

What if rietveld ends with /
Trim it 

[Ryan Tseng, 2016/06/28 21:49:31]

Done.

+		}
+	}
+	return ss
+}
+
 func getDebugBuild(c context.Context, builder, buildNum string) (*buildbotBuild, error) {
 	fname := fmt.Sprintf("%s.%s.json", builder, buildNum)
 	path := filepath.Join("testdata", "buildbot", fname)
@@ -366,6 +398,7 @@ func build(c context.Context, master, builder, buildNum string) (*resp.MiloBuild
 	}
 
 	return &resp.MiloBuild{
+		SourceStamp:   sourcestamp(b),
 		Summary:       summary(b),
 		Components:    components(b),
 		PropertyGroup: properties(b),