> Teach git-commit-graph to read commit graph files and summarize their
> contents.
>
> Use the --read option to verify the contents of a commit graph file in the
> tests.
>
> Signed-off-by: Derrick Stolee
> ---
> Documentation/git-commit-graph.txt | 7 ++
> builtin/commit-graph.c | 55 +++
> commit-graph.c | 138
> -
> commit-graph.h | 25 +++
> t/t5318-commit-graph.sh| 28 ++--
> 5 files changed, 247 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/git-commit-graph.txt
> b/Documentation/git-commit-graph.txt
> index 3f3790d9a8..09aeaf6c82 100644
> --- a/Documentation/git-commit-graph.txt
> +++ b/Documentation/git-commit-graph.txt
> @@ -10,6 +10,7 @@ SYNOPSIS
>
> [verse]
> 'git commit-graph' --write [--pack-dir ]
> +'git commit-graph' --read [--pack-dir ]
Again, what does this option do?
> EXAMPLES
>
> @@ -20,6 +21,12 @@ EXAMPLES
> $ git commit-graph --write
>
>
> +* Read basic information from a graph file.
> ++
> +
> +$ git commit-graph --read --graph-hash=
> +
> +
> GIT
> ---
> Part of the linkgit:git[1] suite
> diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
> index 7affd512f1..218740b1f8 100644
> --- a/builtin/commit-graph.c
> +++ b/builtin/commit-graph.c
> +int close_commit_graph(struct commit_graph *g)
static, perhaps? I see it's declared as extern in the headeer file
below, but I don't see it called outside of this source file by the
end of the patch series.
> +{
> + if (g->graph_fd < 0)
> + return 0;
> +
> + munmap((void *)g->data, g->data_len);
> + g->data = 0;
> +
> + close(g->graph_fd);
> + g->graph_fd = -1;
> +
> + return 1;
> +}
> +
> +static void free_commit_graph(struct commit_graph **g)
> +{
> + if (!g || !*g)
> + return;
> +
> + close_commit_graph(*g);
> +
> + free(*g);
> + *g = NULL;
> +}
> +
> +struct commit_graph *load_commit_graph_one(const char *graph_file, const
> char *pack_dir)
> +{
> + void *graph_map;
> + const unsigned char *data;
> + struct commit_graph_header *hdr;
> + size_t graph_size;
> + struct stat st;
> + uint32_t i;
> + struct commit_graph *graph;
> + int fd = git_open(graph_file);
> + uint64_t last_chunk_offset;
> + uint32_t last_chunk_id;
> +
> + if (fd < 0)
> + return 0;
> + if (fstat(fd, &st)) {
> + close(fd);
> + return 0;
> + }
> + graph_size = xsize_t(st.st_size);
> +
> + if (graph_size < GRAPH_MIN_SIZE) {
> + close(fd);
> + die("graph file %s is too small", graph_file);
> + }
> + graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
> + data = (const unsigned char *)graph_map;
> +
> + hdr = graph_map;
> + if (ntohl(hdr->graph_signature) != GRAPH_SIGNATURE) {
> + uint32_t signature = ntohl(hdr->graph_signature);
> + munmap(graph_map, graph_size);
> + close(fd);
> + die("graph signature %X does not match signature %X",
> + signature, GRAPH_SIGNATURE);
> + }
> + if (hdr->graph_version != GRAPH_VERSION) {
> + unsigned char version = hdr->graph_version;
> + munmap(graph_map, graph_size);
> + close(fd);
> + die("graph version %X does not match version %X",
> + version, GRAPH_VERSION);
> + }
> +
> + graph = alloc_commit_graph(strlen(pack_dir) + 1);
> +
> + graph->hdr = hdr;
> + graph->graph_fd = fd;
> + graph->data = graph_map;
> + graph->data_len = graph_size;
> +
> + last_chunk_id = 0;
> + last_chunk_offset = (uint64_t)sizeof(*hdr);
> + for (i = 0; i < hdr->num_chunks; i++) {
> + uint32_t chunk_id = ntohl(*(uint32_t*)(data + sizeof(*hdr) + 12
> * i));
> + uint64_t chunk_offset1 = ntohl(*(uint32_t*)(data + sizeof(*hdr)
> + 12 * i + 4));
> + uint32_t chunk_offset2 = ntohl(*(uint32_t*)(data + sizeof(*hdr)
> + 12 * i + 8));
There are a lot of magic number in these three lines, but at least
they are all multiples of 4.
> + uint64_t chunk_offset = (chunk_offset1 << 32) | chunk_offset2;
> +
> + if (chunk_offset > graph_size - GIT_MAX_RAWSZ)
> + die("improper chunk offset %08x%08x",
> (uint32_t)(chunk_offset >> 32),
> + (uint32_t)chunk_offset);
> +
> + switch (chunk_id) {
> + case GRAPH_CHUNKID_OIDFANOUT:
> + graph->chunk_oid_fanout = data + chunk_offset;
> + break;
> +
> + case GRAPH_CHUNKID_OIDLOOKUP:
> +
