app/build: include commit date in JSON output

This adds an RFC 3339 commit date for each revision represented in the
mode=json output of the dashboard. This is shown on the HTML version
of the dashboard, so it's already readily available, and its useful
when scraping the dashboard.

Change-Id: I7683ab76505b3dcd2395f54ec6f904a4a8d56617
Reviewed-on: https://go-review.googlesource.com/9012
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

app/build/ui.go

@@ -20,6 +20,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"time"
 
 	"golang.org/x/build/types"
 
@@ -164,6 +165,7 @@ func jsonHandler(w http.ResponseWriter, r *http.Request, data *uiTemplateData) {
 		rev := types.BuildRevision{
 			Repo:     "go",
 			Revision: c.Hash,
+			Date:     c.Time.Format(time.RFC3339),
 			Results:  make([]string, len(data.Builders)),
 		}
 		for i, b := range data.Builders {
@@ -184,6 +186,7 @@ func jsonHandler(w http.ResponseWriter, r *http.Request, data *uiTemplateData) {
 				Repo:       pkgState.Package.Name,
 				Revision:   pkgState.Commit.Hash,
 				GoRevision: goRev,
+				Date:       pkgState.Commit.Time.Format(time.RFC3339),
 				Results:    make([]string, len(data.Builders)),
 			}
 			for i, b := range res.Builders {

types/types.go

@@ -33,6 +33,9 @@ type BuildRevision struct {
 	// Otherwise this is empty.
 	GoRevision string `json:"goRevision,omitempty"`
 
+	// Date is the commit date of this revision, formatted in RFC3339.
+	Date string `json:"date"`
+
 	// Results are the build results for each of the builders in
 	// the same length slice BuildStatus.Builders.
 	// Each string is either "" (if no data), "ok", or the URL to failure logs.