Introduce cmd.Clock() for use in integration tests

If the FAKECLOCK environment variable is set, and the build was in a
test environment, cmd.Clock will return a FakeClock with the time set to
the content of the environment variable.

The choice of the UnixDate format was because `date -d` is a common
choice for shell scripts.

cmd/clock_generic.go

@@ -0,0 +1,14 @@
+// +build !integration
+
+package cmd
+
+import "github.com/letsencrypt/boulder/Godeps/_workspace/src/github.com/jmhodges/clock"
+
+// Clock functions similarly to clock.Default(), but the returned value can be
+// changed using the FAKECLOCK environment variable if the 'integration' build
+// flag is set.
+//
+// This function returns the default Clock.
+func Clock() clock.Clock {
+	return clock.Default()
+}

cmd/clock_integration.go

@@ -0,0 +1,30 @@
+// +build integration
+
+package cmd
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/letsencrypt/boulder/Godeps/_workspace/src/github.com/jmhodges/clock"
+	blog "github.com/letsencrypt/boulder/log"
+)
+
+// Clock functions similarly to clock.Default(), but the returned value can be
+// changed using the FAKECLOCK environment variable if the 'integration' build
+// flag is set.
+//
+// The FAKECLOCK env var is in the time.UnixDate format, returned by `date -d`.
+func Clock() clock.Clock {
+	if tgt := os.Getenv("FAKECLOCK"); tgt != "" {
+		targetTime, err := time.Parse(tgt, time.UnixDate)
+		FailOnError(err, fmt.Sprintf("cmd.Clock: bad format for FAKECLOCK: %v\n", err))
+
+		cl := clock.NewFake()
+		cl.Set(targetTime)
+		blog.GetAuditLogger().Notice(fmt.Sprintf("Time was set to %v via FAKECLOCK", targetTime))
+		return cl
+	}
+	return clock.Default()
+}

cmd/expiration-mailer/main.go

@@ -335,7 +335,7 @@ func main() {
 			emailTemplate: tmpl,
 			nagTimes:      nags,
 			limit:         c.Mailer.CertLimit,
-			clk:           clock.Default(),
+			clk:           cmd.Clock(),
 		}
 
 		auditlogger.Info("expiration-mailer: Starting")

test/startservers.py

@@ -38,7 +38,7 @@ def install(race_detection):
     # BUILD_ID.
     cmd = "make GO_BUILD_FLAGS=''  "
     if race_detection:
-        cmd = "make GO_BUILD_FLAGS=-race"
+        cmd = "make GO_BUILD_FLAGS='-race -tags integration'"
 
     return subprocess.call(cmd, shell=True) == 0