Add developer-only toggle to print all errors

When developing, we often want to see errors that we don't want in the
final output to a regular user.
Even though all errors are always logged to dump.log in the generated
archive, it is more convenient to see them straigh away in stderr,
without needing to go open the dump archive.

main.go

@@ -35,6 +35,11 @@ var (
 	printVersion    = flag.Bool("version", false, "print version and exit")
 )
 
+// showAllErrors enables printing of ignorable errors, suitable for debugging.
+// This is intentionally not exposed as a flag, and shall stay intentionally
+// undocumented, used for development only.
+var _, showAllErrors = os.LookupEnv("FH_SYSTEM_DUMP_TOOL_DEBUG")
+
 // GetProjects returns a list of project names visible by the current logged in
 // user.
 func GetProjects(runner Runner) ([]string, error) {
@@ -162,7 +167,7 @@ func main() {
 	errs := RunAllDumpTasks(runner, basePath, *concurrentTasks, os.Stderr)
 
 	for _, err := range errs {
-		if ierr, ok := err.(IgnorableError); ok && ierr.Ignore() {
+		if ierr, ok := err.(IgnorableError); !showAllErrors && ok && ierr.Ignore() {
 			fileOnlyLogger.Printf("Task error: %v", err)
 			continue
 		}