.tools: Run 'go fmt ./...' on each commit

Instead of just checking the tip, run 'go fmt ./...' on each commit in
the series.  This makes sure we catch errors with earlier commits even
if they were fixed by subsequent commits.

Signed-off-by: W. Trevor King <wking@tremily.us>

Author: wking

.tools/validate.go

@@ -46,6 +46,9 @@ var DefaultRules = []ValidateRule{
 	func(c CommitEntry) (vr ValidateResult) {
 		return ExecTree(c, "go", "vet", "./...")
 	},
+	func(c CommitEntry) (vr ValidateResult) {
+		return ExecTree(c, "go", "fmt", "./...")
+	},
 	func(c CommitEntry) (vr ValidateResult) {
 		vr = ExecTree(c, os.ExpandEnv("$HOME/gopath/bin/golint"), "./...")
 		if len(vr.Detail) > 0 {