[PATCH v4 00/19] Adds reftable library code from https://github.com/hanwen/reftable.

["Han-Wen Nienhuys via GitGitGadget" <gitgitgadget@gmail.com>]

The reftable format is described in Documentation/technical/reftable.txt.

This is a fully reentrant implementation of reading and writing the reftable
file format, and should be suitable for embedding in libgit2 too. It does
not hook the code up to git to function as a ref storage backend yet.

v4:

 * fixes by Carlo Belón.
 * remove RFC from LICENSE commit.

Han-Wen Nienhuys (19):
  hash.h: provide constants for the hash IDs
  reftable: add LICENSE
  reftable: add error related functionality
  reftable: utility functions
  reftable: add blocksource, an abstraction for random access reads
  reftable: (de)serialization for the polymorphic record type.
  Provide zlib's uncompress2 from compat/zlib-compat.c
  reftable: reading/writing blocks
  reftable: a generic binary tree implementation
  reftable: write reftable files
  reftable: generic interface to tables
  reftable: read reftable files
  reftable: reftable file level tests
  reftable: add a heap-based priority queue for reftable records
  reftable: add merged table view
  reftable: implement refname validation
  reftable: implement stack, a mutable database of reftable files.
  reftable: add dump utility
  Add "test-tool dump-reftable" command.

 Makefile                                   |   53 +-
 ci/lib.sh                                  |    1 +
 compat/.gitattributes                      |    1 +
 compat/zlib-uncompress2.c                  |   95 ++
 config.mak.uname                           |    5 +
 configure.ac                               |   13 +
 contrib/buildsystems/CMakeLists.txt        |   14 +-
 contrib/buildsystems/Generators/Vcxproj.pm |   11 +-
 hash.h                                     |    6 +
 object-file.c                              |    7 +-
 reftable/LICENSE                           |   31 +
 reftable/basics.c                          |  128 ++
 reftable/basics.h                          |   60 +
 reftable/basics_test.c                     |   98 ++
 reftable/block.c                           |  437 ++++++
 reftable/block.h                           |  127 ++
 reftable/block_test.c                      |  120 ++
 reftable/blocksource.c                     |  148 +++
 reftable/blocksource.h                     |   22 +
 reftable/constants.h                       |   21 +
 reftable/dump.c                            |  107 ++
 reftable/error.c                           |   41 +
 reftable/generic.c                         |  169 +++
 reftable/generic.h                         |   32 +
 reftable/iter.c                            |  194 +++
 reftable/iter.h                            |   69 +
 reftable/merged.c                          |  362 +++++
 reftable/merged.h                          |   38 +
 reftable/merged_test.c                     |  468 +++++++
 reftable/pq.c                              |  105 ++
 reftable/pq.h                              |   33 +
 reftable/pq_test.c                         |   82 ++
 reftable/publicbasics.c                    |   65 +
 reftable/reader.c                          |  801 +++++++++++
 reftable/reader.h                          |   64 +
 reftable/readwrite_test.c                  |  652 +++++++++
 reftable/record.c                          | 1212 +++++++++++++++++
 reftable/record.h                          |  139 ++
 reftable/record_test.c                     |  412 ++++++
 reftable/refname.c                         |  209 +++
 reftable/refname.h                         |   29 +
 reftable/refname_test.c                    |  102 ++
 reftable/reftable-blocksource.h            |   49 +
 reftable/reftable-error.h                  |   62 +
 reftable/reftable-generic.h                |   47 +
 reftable/reftable-iterator.h               |   39 +
 reftable/reftable-malloc.h                 |   18 +
 reftable/reftable-merged.h                 |   72 +
 reftable/reftable-reader.h                 |  101 ++
 reftable/reftable-record.h                 |  114 ++
 reftable/reftable-stack.h                  |  128 ++
 reftable/reftable-tests.h                  |   23 +
 reftable/reftable-writer.h                 |  148 +++
 reftable/reftable.c                        |  115 ++
 reftable/stack.c                           | 1396 ++++++++++++++++++++
 reftable/stack.h                           |   41 +
 reftable/stack_test.c                      |  953 +++++++++++++
 reftable/system.h                          |   32 +
 reftable/test_framework.c                  |   23 +
 reftable/test_framework.h                  |   53 +
 reftable/tree.c                            |   63 +
 reftable/tree.h                            |   34 +
 reftable/tree_test.c                       |   61 +
 reftable/writer.c                          |  690 ++++++++++
 reftable/writer.h                          |   50 +
 t/helper/test-reftable.c                   |   21 +
 t/helper/test-tool.c                       |    4 +-
 t/helper/test-tool.h                       |    2 +
 t/t0032-reftable-unittest.sh               |   15 +
 69 files changed, 11125 insertions(+), 12 deletions(-)
 create mode 100644 compat/.gitattributes
 create mode 100644 compat/zlib-uncompress2.c
 create mode 100644 reftable/LICENSE
 create mode 100644 reftable/basics.c
 create mode 100644 reftable/basics.h
 create mode 100644 reftable/basics_test.c
 create mode 100644 reftable/block.c
 create mode 100644 reftable/block.h
 create mode 100644 reftable/block_test.c
 create mode 100644 reftable/blocksource.c
 create mode 100644 reftable/blocksource.h
 create mode 100644 reftable/constants.h
 create mode 100644 reftable/dump.c
 create mode 100644 reftable/error.c
 create mode 100644 reftable/generic.c
 create mode 100644 reftable/generic.h
 create mode 100644 reftable/iter.c
 create mode 100644 reftable/iter.h
 create mode 100644 reftable/merged.c
 create mode 100644 reftable/merged.h
 create mode 100644 reftable/merged_test.c
 create mode 100644 reftable/pq.c
 create mode 100644 reftable/pq.h
 create mode 100644 reftable/pq_test.c
 create mode 100644 reftable/publicbasics.c
 create mode 100644 reftable/reader.c
 create mode 100644 reftable/reader.h
 create mode 100644 reftable/readwrite_test.c
 create mode 100644 reftable/record.c
 create mode 100644 reftable/record.h
 create mode 100644 reftable/record_test.c
 create mode 100644 reftable/refname.c
 create mode 100644 reftable/refname.h
 create mode 100644 reftable/refname_test.c
 create mode 100644 reftable/reftable-blocksource.h
 create mode 100644 reftable/reftable-error.h
 create mode 100644 reftable/reftable-generic.h
 create mode 100644 reftable/reftable-iterator.h
 create mode 100644 reftable/reftable-malloc.h
 create mode 100644 reftable/reftable-merged.h
 create mode 100644 reftable/reftable-reader.h
 create mode 100644 reftable/reftable-record.h
 create mode 100644 reftable/reftable-stack.h
 create mode 100644 reftable/reftable-tests.h
 create mode 100644 reftable/reftable-writer.h
 create mode 100644 reftable/reftable.c
 create mode 100644 reftable/stack.c
 create mode 100644 reftable/stack.h
 create mode 100644 reftable/stack_test.c
 create mode 100644 reftable/system.h
 create mode 100644 reftable/test_framework.c
 create mode 100644 reftable/test_framework.h
 create mode 100644 reftable/tree.c
 create mode 100644 reftable/tree.h
 create mode 100644 reftable/tree_test.c
 create mode 100644 reftable/writer.c
 create mode 100644 reftable/writer.h
 create mode 100644 t/helper/test-reftable.c
 create mode 100755 t/t0032-reftable-unittest.sh


base-commit: 106298f7f9cca4158a980de149ef217751e1f943
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1081%2Fhanwen%2Fjust-library-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1081/hanwen/just-library-v4
Pull-Request: https://github.com/git/git/pull/1081

Range-diff vs v3:

  1:  b2f8dc32bfc =  1:  9cc44f78377 hash.h: provide constants for the hash IDs
  2:  2597ddfeae1 !  2:  6a5ee5db472 reftable: RFC: add LICENSE
     @@ Metadata
      Author: Han-Wen Nienhuys <hanwen@google.com>
      
       ## Commit message ##
     -    reftable: RFC: add LICENSE
     +    reftable: add LICENSE
      
          The objective of this code is to be usable as a C library, so it can be reused
          in libgit2.
  3:  41b1ff1293f !  3:  bf51bc9ab0c reftable: add error related functionality
     @@ Commit message
          reftable: add error related functionality
      
          The reftable/ directory is structured as a library, so it cannot
     -    crash on misuse. Instead, it returns an error codes.
     +    crash on misuse. Instead, it returns an error code.
      
     -    In addition, the error code can be used to signal conditions from lower levels
     -    of the library to be handled by higher levels of the library. For example, a
     -    transaction might legitimately write an empty reftable file, but in that case,
     -    we'd want to shortcut the transaction overhead.
     +    In addition to signaling errors, the error code can be used to signal
     +    conditions from lower levels of the library to be handled by higher
     +    levels of the library. For example, in a transaction we might
     +    legitimately write an empty reftable file, but in that case, we want to
     +    shortcut the transaction.
      
          Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
      
  4:  c03043c5e63 !  4:  318e7ad41e5 reftable: utility functions
     @@ reftable/publicbasics.c (new)
      +#include "basics.h"
      +#include "system.h"
      +
     -+static void *(*reftable_malloc_ptr)(size_t sz) = &malloc;
     -+static void *(*reftable_realloc_ptr)(void *, size_t) = &realloc;
     -+static void (*reftable_free_ptr)(void *) = &free;
     ++static void *(*reftable_malloc_ptr)(size_t sz);
     ++static void *(*reftable_realloc_ptr)(void *, size_t);
     ++static void (*reftable_free_ptr)(void *);
      +
      +void *reftable_malloc(size_t sz)
      +{
     -+	return (*reftable_malloc_ptr)(sz);
     ++	if (reftable_malloc_ptr)
     ++		return (*reftable_malloc_ptr)(sz);
     ++	return malloc(sz);
      +}
      +
      +void *reftable_realloc(void *p, size_t sz)
      +{
     -+	return (*reftable_realloc_ptr)(p, sz);
     ++	if (reftable_realloc_ptr)
     ++		return (*reftable_realloc_ptr)(p, sz);
     ++	return realloc(p, sz);
      +}
      +
      +void reftable_free(void *p)
      +{
     -+	reftable_free_ptr(p);
     ++	if (reftable_free_ptr)
     ++		reftable_free_ptr(p);
     ++	else
     ++		free(p);
      +}
      +
      +void *reftable_calloc(size_t sz)
  5:  317a6aaa357 =  5:  80036f93e2e reftable: add blocksource, an abstraction for random access reads
  6:  55e66b7a74f =  6:  f2cd2876265 reftable: (de)serialization for the polymorphic record type.
  7:  4f6ecd3646a !  7:  6cbc2f758df Provide zlib's uncompress2 from compat/zlib-compat.c
     @@ config.mak.uname: ifeq ($(uname_S),FreeBSD)
       	NO_STRCASESTR = YesPlease
       	NO_MEMMEM = YesPlease
       	USE_ST_TIMESPEC = YesPlease
     +@@ config.mak.uname: ifeq ($(uname_S),Interix)
     + 	endif
     + endif
     + ifeq ($(uname_S),Minix)
     ++	NO_UNCOMPRESS2 = YesPlease
     + 	NO_IPV6 = YesPlease
     + 	NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease
     + 	NO_NSEC = YesPlease
      
       ## configure.ac ##
      @@ configure.ac: AC_LINK_IFELSE([ZLIBTEST_SRC],
  8:  04f2d74df51 !  8:  1002d6f526c reftable: reading/writing blocks
     @@ Commit message
      
          This commit provides the logic to read and write these blocks.
      
     +    Helped-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
          Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
      
       ## Makefile ##
     @@ reftable/block.c (new)
      +
      +int block_writer_finish(struct block_writer *w)
      +{
     -+	int i = 0;
     ++	int i;
      +	for (i = 0; i < w->restart_len; i++) {
      +		put_be24(w->buf + w->next, w->restarts[i]);
      +		w->next += 3;
     @@ reftable/block.c (new)
      +
      +	if (block_writer_type(w) == BLOCK_TYPE_LOG) {
      +		int block_header_skip = 4 + w->header_off;
     -+		uint8_t *compressed = NULL;
     -+		int zresult = 0;
      +		uLongf src_len = w->next - block_header_skip;
     -+		size_t dest_cap = src_len;
     ++		uLongf dest_cap = src_len * 1.001 + 12;
      +
     -+		compressed = reftable_malloc(dest_cap);
     ++		uint8_t *compressed = reftable_malloc(dest_cap);
      +		while (1) {
      +			uLongf out_dest_len = dest_cap;
     -+
     -+			zresult = compress2(compressed, &out_dest_len,
     -+					    w->buf + block_header_skip, src_len,
     -+					    9);
     -+			if (zresult == Z_BUF_ERROR) {
     ++			int zresult = compress2(compressed, &out_dest_len,
     ++						w->buf + block_header_skip,
     ++						src_len, 9);
     ++			if (zresult == Z_BUF_ERROR && dest_cap < LONG_MAX) {
      +				dest_cap *= 2;
      +				compressed =
      +					reftable_realloc(compressed, dest_cap);
     -+				continue;
     ++				if (compressed)
     ++					continue;
      +			}
      +
      +			if (Z_OK != zresult) {
  9:  f6c2da61208 =  9:  96e490ac32c reftable: a generic binary tree implementation
 10:  277a1f662e3 = 10:  daf9cc897d1 reftable: write reftable files
 11:  f97182dec1f = 11:  c9a5813b211 reftable: generic interface to tables
 12:  13de5d03a71 ! 12:  854b30268b6 reftable: read reftable files
     @@ reftable/reader.c (new)
      +	return 0;
      +}
      +
     -+int reader_seek(struct reftable_reader *r, struct reftable_iterator *it,
     -+		struct reftable_record *rec)
     ++static int reader_seek(struct reftable_reader *r, struct reftable_iterator *it,
     ++		       struct reftable_record *rec)
      +{
      +	uint8_t typ = reftable_record_type(rec);
      +
     @@ reftable/reader.h (new)
      +
      +int init_reader(struct reftable_reader *r, struct reftable_block_source *source,
      +		const char *name);
     -+int reader_seek(struct reftable_reader *r, struct reftable_iterator *it,
     -+		struct reftable_record *rec);
      +void reader_close(struct reftable_reader *r);
      +const char *reader_name(struct reftable_reader *r);
      +
 13:  8efc3c2b6ab = 13:  c0d0427d52c reftable: reftable file level tests
 14:  e89b16a37e6 ! 14:  6e5ee043083 reftable: add a heap-based priority queue for reftable records
     @@ reftable/pq_test.c (new)
      +
      +void merged_iter_pqueue_check(struct merged_iter_pqueue pq)
      +{
     -+	int i = 0;
     ++	int i;
      +	for (i = 1; i < pq.len; i++) {
      +		int parent = (i - 1) / 2;
      +
     -+		assert(pq_less(&pq.heap[parent], &pq.heap[i]));
     ++		EXPECT(pq_less(&pq.heap[parent], &pq.heap[i]));
      +	}
      +}
      +
 15:  40a91b14be8 ! 15:  0b86f6c2327 reftable: add merged table view
     @@ reftable/merged.h (new)
      +	struct reftable_table *stack;
      +	size_t stack_len;
      +	uint32_t hash_id;
     ++
     ++	/* If unset, produce deletions. This is useful for compaction. For the
     ++	 * full stack, deletions should be produced. */
      +	int suppress_deletions;
      +
      +	uint64_t min;
     @@ reftable/merged_test.c (new)
      +	reftable_writer_free(w);
      +}
      +
     ++static void write_test_log_table(struct strbuf *buf,
     ++				 struct reftable_log_record logs[], int n,
     ++				 uint64_t update_index)
     ++{
     ++	int i = 0;
     ++	int err;
     ++
     ++	struct reftable_write_options opts = {
     ++		.block_size = 256,
     ++		.exact_log_message = 1,
     ++	};
     ++	struct reftable_writer *w = NULL;
     ++	w = reftable_new_writer(&strbuf_add_void, buf, &opts);
     ++	reftable_writer_set_limits(w, update_index, update_index);
     ++
     ++	for (i = 0; i < n; i++) {
     ++		int err = reftable_writer_add_log(w, &logs[i]);
     ++		EXPECT_ERR(err);
     ++	}
     ++
     ++	err = reftable_writer_close(w);
     ++	EXPECT_ERR(err);
     ++
     ++	reftable_writer_free(w);
     ++}
     ++
      +static struct reftable_merged_table *
      +merged_table_from_records(struct reftable_ref_record **refs,
      +			  struct reftable_block_source **source,
     @@ reftable/merged_test.c (new)
      +	int i = 0;
      +
      +	EXPECT_ERR(err);
     ++	EXPECT(reftable_merged_table_hash_id(mt) == GIT_SHA1_FORMAT_ID);
     ++	EXPECT(reftable_merged_table_min_update_index(mt) == 1);
     ++
      +	while (len < 100) { /* cap loops/recursion. */
      +		struct reftable_ref_record ref = { NULL };
      +		int err = reftable_iterator_next_ref(&it, &ref);
     @@ reftable/merged_test.c (new)
      +	reftable_free(bs);
      +}
      +
     ++static struct reftable_merged_table *
     ++merged_table_from_log_records(struct reftable_log_record **logs,
     ++			      struct reftable_block_source **source,
     ++			      struct reftable_reader ***readers, int *sizes,
     ++			      struct strbuf *buf, int n)
     ++{
     ++	int i = 0;
     ++	struct reftable_merged_table *mt = NULL;
     ++	int err;
     ++	struct reftable_table *tabs =
     ++		reftable_calloc(n * sizeof(struct reftable_table));
     ++	*readers = reftable_calloc(n * sizeof(struct reftable_reader *));
     ++	*source = reftable_calloc(n * sizeof(**source));
     ++	for (i = 0; i < n; i++) {
     ++		write_test_log_table(&buf[i], logs[i], sizes[i], i + 1);
     ++		block_source_from_strbuf(&(*source)[i], &buf[i]);
     ++
     ++		err = reftable_new_reader(&(*readers)[i], &(*source)[i],
     ++					  "name");
     ++		EXPECT_ERR(err);
     ++		reftable_table_from_reader(&tabs[i], (*readers)[i]);
     ++	}
     ++
     ++	err = reftable_new_merged_table(&mt, tabs, n, GIT_SHA1_FORMAT_ID);
     ++	EXPECT_ERR(err);
     ++	return mt;
     ++}
     ++
     ++static void test_merged_logs(void)
     ++{
     ++	uint8_t hash1[GIT_SHA1_RAWSZ] = { 1 };
     ++	uint8_t hash2[GIT_SHA1_RAWSZ] = { 2 };
     ++	uint8_t hash3[GIT_SHA1_RAWSZ] = { 3 };
     ++	struct reftable_log_record r1[] = {
     ++		{
     ++			.refname = "a",
     ++			.update_index = 2,
     ++			.value_type = REFTABLE_LOG_UPDATE,
     ++			.value.update = {
     ++				.old_hash = hash2,
     ++				/* deletion */
     ++				.name = "jane doe",
     ++				.email = "jane@invalid",
     ++				.message = "message2",
     ++			}
     ++		},
     ++		{
     ++			.refname = "a",
     ++			.update_index = 1,
     ++			.value_type = REFTABLE_LOG_UPDATE,
     ++			.value.update = {
     ++				.old_hash = hash1,
     ++				.new_hash = hash2,
     ++				.name = "jane doe",
     ++				.email = "jane@invalid",
     ++				.message = "message1",
     ++			}
     ++		},
     ++	};
     ++	struct reftable_log_record r2[] = {
     ++		{
     ++			.refname = "a",
     ++			.update_index = 3,
     ++			.value_type = REFTABLE_LOG_UPDATE,
     ++			.value.update = {
     ++				.new_hash = hash3,
     ++				.name = "jane doe",
     ++				.email = "jane@invalid",
     ++				.message = "message3",
     ++			}
     ++		},
     ++	};
     ++	struct reftable_log_record r3[] = {
     ++		{
     ++			.refname = "a",
     ++			.update_index = 2,
     ++			.value_type = REFTABLE_LOG_DELETION,
     ++		},
     ++	};
     ++	struct reftable_log_record want[] = {
     ++		r2[0],
     ++		r3[0],
     ++		r1[1],
     ++	};
     ++
     ++	struct reftable_log_record *logs[] = { r1, r2, r3 };
     ++	int sizes[3] = { 2, 1, 1 };
     ++	struct strbuf bufs[3] = { STRBUF_INIT, STRBUF_INIT, STRBUF_INIT };
     ++	struct reftable_block_source *bs = NULL;
     ++	struct reftable_reader **readers = NULL;
     ++	struct reftable_merged_table *mt = merged_table_from_log_records(
     ++		logs, &bs, &readers, sizes, bufs, 3);
     ++
     ++	struct reftable_iterator it = { NULL };
     ++	int err = reftable_merged_table_seek_log(mt, &it, "a");
     ++	struct reftable_log_record *out = NULL;
     ++	size_t len = 0;
     ++	size_t cap = 0;
     ++	int i = 0;
     ++
     ++	EXPECT_ERR(err);
     ++	EXPECT(reftable_merged_table_hash_id(mt) == GIT_SHA1_FORMAT_ID);
     ++	EXPECT(reftable_merged_table_min_update_index(mt) == 1);
     ++
     ++	while (len < 100) { /* cap loops/recursion. */
     ++		struct reftable_log_record log = { NULL };
     ++		int err = reftable_iterator_next_log(&it, &log);
     ++		if (err > 0) {
     ++			break;
     ++		}
     ++		if (len == cap) {
     ++			cap = 2 * cap + 1;
     ++			out = reftable_realloc(
     ++				out, sizeof(struct reftable_log_record) * cap);
     ++		}
     ++		out[len++] = log;
     ++	}
     ++	reftable_iterator_destroy(&it);
     ++
     ++	EXPECT(ARRAY_SIZE(want) == len);
     ++	for (i = 0; i < len; i++) {
     ++		EXPECT(reftable_log_record_equal(&want[i], &out[i],
     ++						 GIT_SHA1_RAWSZ));
     ++	}
     ++
     ++	err = reftable_merged_table_seek_log_at(mt, &it, "a", 2);
     ++	EXPECT_ERR(err);
     ++	reftable_log_record_release(&out[0]);
     ++	err = reftable_iterator_next_log(&it, &out[0]);
     ++	EXPECT_ERR(err);
     ++	EXPECT(reftable_log_record_equal(&out[0], &r3[0], GIT_SHA1_RAWSZ));
     ++	reftable_iterator_destroy(&it);
     ++
     ++	for (i = 0; i < len; i++) {
     ++		reftable_log_record_release(&out[i]);
     ++	}
     ++	reftable_free(out);
     ++
     ++	for (i = 0; i < 3; i++) {
     ++		strbuf_release(&bufs[i]);
     ++	}
     ++	readers_destroy(readers, 3);
     ++	reftable_merged_table_free(mt);
     ++	reftable_free(bs);
     ++}
     ++
      +static void test_default_write_opts(void)
      +{
      +	struct reftable_write_options opts = { 0 };
     @@ reftable/merged_test.c (new)
      +
      +int merged_test_main(int argc, const char *argv[])
      +{
     ++	RUN_TEST(test_merged_logs);
      +	RUN_TEST(test_merged_between);
      +	RUN_TEST(test_merged);
      +	RUN_TEST(test_default_write_opts);
 16:  46c2ddf07cf = 16:  c600e1f975c reftable: implement refname validation
 17:  3db887bc078 ! 17:  55dacc6760f reftable: implement stack, a mutable database of reftable files.
     @@ reftable/stack_test.c (new)
      +	return len;
      +}
      +
     -+// Work linenumber into the tempdir, so we can see which tests forget to
     -+// cleanup.
     ++/*
     ++ * Work linenumber into the tempdir, so we can see which tests forget to
     ++ * cleanup.
     ++ */
      +static char *get_tmp_template(int linenumber)
      +{
      +	const char *tmp = getenv("TMPDIR");
     @@ reftable/stack_test.c (new)
      +	err = reftable_new_stack(&st, dir, cfg);
      +	EXPECT_ERR(err);
      +
     ++	st->disable_auto_compact = 1; /* call manually below for coverage. */
      +	for (i = 0; i < N; i++) {
      +		char name[100];
      +		struct reftable_ref_record ref = {
     @@ reftable/stack_test.c (new)
      +		err = reftable_stack_add(st, &write_test_ref, &ref);
      +		EXPECT_ERR(err);
      +
     ++		err = reftable_stack_auto_compact(st);
      +		EXPECT(i < 3 || st->merged->stack_len < 2 * fastlog2(i));
      +	}
      +
     @@ reftable/stack_test.c (new)
      +
      +static void unclean_stack_close(struct reftable_stack *st)
      +{
     -+	// break abstraction boundary to simulate unclean shutdown.
     ++	/* break abstraction boundary to simulate unclean shutdown. */
      +	int i = 0;
      +	for (; i < st->readers_len; i++) {
      +		reftable_reader_free(st->readers[i]);
 18:  795a15000fb = 18:  2f825cdb2d4 reftable: add dump utility
 19:  7b3215aef39 = 19:  c8428cb0df8 Add "test-tool dump-reftable" command.

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