Retry pmtiles extract/merge on failure, not just on the first try

lib/maptool/pmtiles_builder.rb

@@ -629,9 +629,16 @@ module Maptool
     end
     private_class_method :command_output
 
-    def self.run_pmtiles!(*args)
-      stdout, stderr, status = Open3.capture3(pmtiles_bin, *args)
-      raise BuildError, "pmtiles exited with status #{status.exitstatus}: #{command_output(stdout, stderr)}" unless status.success?
+    # extract/merge stream tens of GB over HTTP range requests; retry a
+    # transient failure (e.g. a mid-transfer HTTP/2 stream reset from the
+    # remote) a couple times before giving up, rather than forcing a full
+    # re-download on every hiccup.
+    def self.run_pmtiles!(*args, attempts: 3)
+      attempts.times do |i|
+        stdout, stderr, status = Open3.capture3(pmtiles_bin, *args)
+        return if status.success?
+        raise BuildError, "pmtiles exited with status #{status.exitstatus}: #{command_output(stdout, stderr)}" if i == attempts - 1
+      end
     rescue Errno::ENOENT, Errno::EACCES => e
       raise BuildError, "could not run '#{pmtiles_bin}' (#{e.message}) — is go-pmtiles installed and on PATH? See docs/development.adoc."
     end