Merge branch 'ps/reftable-drop-generic'

The code in the reftable library has been cleaned up by discarding
unused "generic" interface.

* ps/reftable-drop-generic:
  reftable: mark unused parameters in empty iterator functions
  reftable/generic: drop interface
  t/helper: refactor to not use `struct reftable_table`
  t/helper: use `hash_to_hex_algop()` to print hashes
  t/helper: inline printing of reftable records
  t/helper: inline `reftable_table_print()`
  t/helper: inline `reftable_stack_print_directory()`
  t/helper: inline `reftable_reader_print_file()`
  t/helper: inline `reftable_dump_main()`
  reftable/dump: drop unused `compact_stack()`
  reftable/generic: move generic iterator code into iterator interface
  reftable/iter: drop double-checking logic
  reftable/stack: open-code reading refs
  reftable/merged: stop using generic tables in the merged table
  reftable/merged: rename `reftable_new_merged_table()`
  reftable/merged: expose functions to initialize iterators

Author: gitster

Makefile

@@ -2678,13 +2678,11 @@ REFTABLE_OBJS += reftable/merged.o
 REFTABLE_OBJS += reftable/pq.o
 REFTABLE_OBJS += reftable/reader.o
 REFTABLE_OBJS += reftable/record.o
-REFTABLE_OBJS += reftable/generic.o
 REFTABLE_OBJS += reftable/stack.o
 REFTABLE_OBJS += reftable/tree.o
 REFTABLE_OBJS += reftable/writer.o
 
 REFTABLE_TEST_OBJS += reftable/block_test.o
-REFTABLE_TEST_OBJS += reftable/dump.o
 REFTABLE_TEST_OBJS += reftable/stack_test.o
 REFTABLE_TEST_OBJS += reftable/test_framework.o