On 12/3/2020 11:16 AM, Derrick Stolee via GitGitGadget wrote:

From: Derrick Stolee <redacted>

The previous change introduced read_table_of_contents() in the
chunk-format API, but dropped the duplicate chunk check from the
commit-graph parsing logic. This was done to keep flexibility in the
chunk-format API.

"keep flexibility" is bogus. This is the biggest YAGNI of this
series. Instead, consider the patch below instead which restores
duplicate checks for the commit-graph file AND adds them to the
multi-pack-index file due to the shared API.

This is also roughly half of the added lines from the previous
patch.

Thanks,
-Stolee

-- >8 --

From 0df4959d59d7f9df3e9f6326bb0acb7b84f84980 Mon Sep 17 00:00:00 2001
From: Derrick Stolee <redacted>
Date: Mon, 7 Dec 2020 08:36:42 -0500
Subject: [PATCH] chunk-format: restore duplicate chunk checks

Before refactoring into the chunk-format API, the commit-graph parsing
logic included checks for duplicate chunks. It is unlikely that we would
desire a chunk-based file format that allows duplicate chunk IDs in the
table of contents, so add duplicate checks into
read_table_of_contents().

Signed-off-by: Derrick Stolee <redacted>
---
 chunk-format.c | 15 ++++++++++++++-
 chunk-format.h |  3 +++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/chunk-format.c b/chunk-format.c
index d888ef6ec73..a4891bbd28a 100644
--- a/chunk-format.c
+++ b/chunk-format.c

@@ -57,9 +57,13 @@ int read_table_of_contents(const unsigned char *mfile,
 			   int nr,
 			   void *data)
 {
+	int i;
 	uint32_t chunk_id;
 	const unsigned char *table_of_contents = mfile + toc_offset;
 
+	for (i = 0; i < nr; i++)
+		chunks[i].found = 0;
+
 	while (toc_length--) {
 		int i;
 		uint64_t chunk_offset, next_chunk_offset;

@@ -83,7 +87,16 @@ int read_table_of_contents(const unsigned char *mfile,
 		}
 		for (i = 0; i < nr; i++) {
 			if (chunks[i].id == chunk_id) {
-				int result = chunks[i].read_fn(
+				int result;
+
+				if (chunks[i].found) {
+					error(_("duplicate chunk ID %"PRIx32" found"),
+					      chunk_id);
+					return 1;
+				}
+
+				chunks[i].found = 1;
+				result = chunks[i].read_fn(
 						mfile + chunk_offset,
 						next_chunk_offset - chunk_offset,
 						data);

diff --git a/chunk-format.h b/chunk-format.h
index 7049800f734..de45797223a 100644
--- a/chunk-format.h
+++ b/chunk-format.h

@@ -56,6 +56,9 @@ typedef int (*chunk_read_fn)(const unsigned char *chunk_start,
 struct read_chunk_info {
 	uint32_t id;
 	chunk_read_fn read_fn;
+
+	/* used internally */
+	unsigned found:1;
 };
 
 int read_table_of_contents(const unsigned char *mfile,

-- 
2.29.0.vfs.0.0