gopls/internal/telemetry/cmd/stacks: print double-claimed stacks

Otherwise it can be very hard to guess why two issues' rules
intersect!

Change-Id: I4ac88b9e95f79cf4b2b1f4c8072a6c90c07bb295
Reviewed-on: https://go-review.googlesource.com/c/tools/+/621815
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>

Author: adonovan

Diff for: gopls/internal/telemetry/cmd/stacks/stacks.go

@@ -324,8 +324,8 @@ func main() {
 			}
 
 			if prev := claimedBy[id]; prev != nil && prev != issue {
-				log.Printf("stack %s is claimed by issues #%d and #%d",
-					id, prev.Number, issue.Number)
+				log.Printf("stack %s is claimed by issues #%d and #%d:%s",
+					id, prev.Number, issue.Number, strings.ReplaceAll("\n"+stack, "\n", "\n- "))
 				continue
 			}
 			if false {