[PATCH 0/2] Specify generation number version by config

[PATCH 0/2] Specify generation number version by config

[Derrick Stolee via GitGitGadget]

This is based on ds/chunked-file-api.

Generation number v2 (corrected commit dates) was introduced by
ak/corrected-commit-date. The new data could be opted-out only using the
GIT_TEST_COMMIT_GRAPH_NO_GDAT environment variable.

As this feature gets deployed more widely, servers in particular might want
more control over when this format is used. Add a config option instead.

Thanks, -Stolee

Derrick Stolee (2):
  commit-graph: create local repository pointer
  commit-graph: use config to specify generation type

 Documentation/config/commitgraph.txt |  6 ++++++
 commit-graph.c                       | 31 ++++++++++++++++++----------
 commit-graph.h                       |  1 -
 t/README                             |  3 ---
 t/t5318-commit-graph.sh              |  2 +-
 t/t5324-split-commit-graph.sh        |  4 ++--
 t/t6600-test-reach.sh                |  2 +-
 7 files changed, 30 insertions(+), 19 deletions(-)


base-commit: c4ff24bbb354377a6a7937744fbbef2898243fc7
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-886%2Fderrickstolee%2Fcommit-graph-generation-config-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-886/derrickstolee/commit-graph-generation-config-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/886
-- 
gitgitgadget

[PATCH 1/2] commit-graph: create local repository pointer

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <dstolee@microsoft.com>

The write_commit_graph() method uses 'the_repository' in a few places. A
new need for a repository pointer is coming in the following change, so
group these instances into a local variable 'r' that could eventually
become part of the method signature, if so desired.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 commit-graph.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index b9efeddeab6c..8b07a9a0a6df 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -2155,6 +2155,7 @@ int write_commit_graph(struct object_directory *odb,
 		       enum commit_graph_write_flags flags,
 		       const struct commit_graph_opts *opts)
 {
+	struct repository *r = the_repository;
 	struct write_commit_graph_context *ctx;
 	uint32_t i;
 	int res = 0;
@@ -2162,16 +2163,16 @@ int write_commit_graph(struct object_directory *odb,
 	struct bloom_filter_settings bloom_settings = DEFAULT_BLOOM_FILTER_SETTINGS;
 	struct topo_level_slab topo_levels;
 
-	prepare_repo_settings(the_repository);
-	if (!the_repository->settings.core_commit_graph) {
+	prepare_repo_settings(r);
+	if (!r->settings.core_commit_graph) {
 		warning(_("attempting to write a commit-graph, but 'core.commitGraph' is disabled"));
 		return 0;
 	}
-	if (!commit_graph_compatible(the_repository))
+	if (!commit_graph_compatible(r))
 		return 0;
 
 	ctx = xcalloc(1, sizeof(struct write_commit_graph_context));
-	ctx->r = the_repository;
+	ctx->r = r;
 	ctx->odb = odb;
 	ctx->append = flags & COMMIT_GRAPH_WRITE_APPEND ? 1 : 0;
 	ctx->report_progress = flags & COMMIT_GRAPH_WRITE_PROGRESS ? 1 : 0;
-- 
gitgitgadget

[PATCH 2/2] commit-graph: use config to specify generation type

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <dstolee@microsoft.com>

We have two established generation number versions:

 1: topological levels
 2: corrected commit dates

The corrected commit dates are enabled by default, but they also write
extra data in the GDAT and GDOV chunks. Services that host Git data
might want to have more control over when this feature rolls out than
just updating the Git binaries.

Add a new "commitGraph.generationVersion" config option that specifies
the intended generation number version. If this value is less than 2,
then the GDAT chunk is never written _or read_ from an existing file.

This can replace our use of the GIT_TEST_COMMIT_GRAPH_NO_GDAT
environment variable in the test suite. Remove it.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Documentation/config/commitgraph.txt |  6 ++++++
 commit-graph.c                       | 22 +++++++++++++++-------
 commit-graph.h                       |  1 -
 t/README                             |  3 ---
 t/t5318-commit-graph.sh              |  2 +-
 t/t5324-split-commit-graph.sh        |  4 ++--
 t/t6600-test-reach.sh                |  2 +-
 7 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/Documentation/config/commitgraph.txt b/Documentation/config/commitgraph.txt
index 4582c39fc462..30604e4a4c29 100644
--- a/Documentation/config/commitgraph.txt
+++ b/Documentation/config/commitgraph.txt
@@ -1,3 +1,9 @@
+commitGraph.generationVersion::
+	Specifies the type of generation number version to use when writing
+	or reading the commit-graph file. If version 1 is specified, then
+	the corrected commit dates will not be written or read. Defaults to
+	2.
+
 commitGraph.maxNewFilters::
 	Specifies the default value for the `--max-new-filters` option of `git
 	commit-graph write` (c.f., linkgit:git-commit-graph[1]).
diff --git a/commit-graph.c b/commit-graph.c
index 8b07a9a0a6df..1e9b88c003d7 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -96,6 +96,13 @@ define_commit_slab(commit_graph_data_slab, struct commit_graph_data);
 static struct commit_graph_data_slab commit_graph_data_slab =
 	COMMIT_SLAB_INIT(1, commit_graph_data_slab);
 
+static int get_configured_generation_version(struct repository *r)
+{
+	int version = 2;
+	repo_config_get_int(r, "commitgraph.generationversion", &version);
+	return version;
+}
+
 uint32_t commit_graph_position(const struct commit *c)
 {
 	struct commit_graph_data *data =
@@ -394,10 +401,13 @@ struct commit_graph *parse_commit_graph(struct repository *r,
 	pair_chunk(cf, GRAPH_CHUNKID_DATA, &graph->chunk_commit_data);
 	pair_chunk(cf, GRAPH_CHUNKID_EXTRAEDGES, &graph->chunk_extra_edges);
 	pair_chunk(cf, GRAPH_CHUNKID_BASE, &graph->chunk_base_graphs);
-	pair_chunk(cf, GRAPH_CHUNKID_GENERATION_DATA,
-		   &graph->chunk_generation_data);
-	pair_chunk(cf, GRAPH_CHUNKID_GENERATION_DATA_OVERFLOW,
-		   &graph->chunk_generation_data_overflow);
+
+	if (get_configured_generation_version(r) >= 2) {
+		pair_chunk(cf, GRAPH_CHUNKID_GENERATION_DATA,
+			&graph->chunk_generation_data);
+		pair_chunk(cf, GRAPH_CHUNKID_GENERATION_DATA_OVERFLOW,
+			&graph->chunk_generation_data_overflow);
+	}
 
 	if (r->settings.commit_graph_read_changed_paths) {
 		pair_chunk(cf, GRAPH_CHUNKID_BLOOMINDEXES,
@@ -1771,8 +1781,6 @@ static int write_commit_graph_file(struct write_commit_graph_context *ctx)
 	add_chunk(cf, GRAPH_CHUNKID_DATA, (hashsz + 16) * ctx->commits.nr,
 		  write_graph_chunk_data);
 
-	if (git_env_bool(GIT_TEST_COMMIT_GRAPH_NO_GDAT, 0))
-		ctx->write_generation_data = 0;
 	if (ctx->write_generation_data)
 		add_chunk(cf, GRAPH_CHUNKID_GENERATION_DATA,
 			  sizeof(uint32_t) * ctx->commits.nr,
@@ -2179,7 +2187,7 @@ int write_commit_graph(struct object_directory *odb,
 	ctx->split = flags & COMMIT_GRAPH_WRITE_SPLIT ? 1 : 0;
 	ctx->opts = opts;
 	ctx->total_bloom_filter_data_size = 0;
-	ctx->write_generation_data = 1;
+	ctx->write_generation_data = (get_configured_generation_version(r) == 2);
 	ctx->num_generation_data_overflows = 0;
 
 	bloom_settings.bits_per_entry = git_env_ulong("GIT_TEST_BLOOM_SETTINGS_BITS_PER_ENTRY",
diff --git a/commit-graph.h b/commit-graph.h
index 97f3497c2790..96c24fb5777d 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -6,7 +6,6 @@
 #include "oidset.h"
 
 #define GIT_TEST_COMMIT_GRAPH "GIT_TEST_COMMIT_GRAPH"
-#define GIT_TEST_COMMIT_GRAPH_NO_GDAT "GIT_TEST_COMMIT_GRAPH_NO_GDAT"
 #define GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE "GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE"
 #define GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS "GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS"
 
diff --git a/t/README b/t/README
index 8a121487279b..c730a7077057 100644
--- a/t/README
+++ b/t/README
@@ -393,9 +393,6 @@ GIT_TEST_COMMIT_GRAPH=<boolean>, when true, forces the commit-graph to
 be written after every 'git commit' command, and overrides the
 'core.commitGraph' setting to true.
 
-GIT_TEST_COMMIT_GRAPH_NO_GDAT=<boolean>, when true, forces the
-commit-graph to be written without generation data chunk.
-
 GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=<boolean>, when true, forces
 commit-graph write to compute and write changed path Bloom filters for
 every 'git commit-graph write', as if the `--changed-paths` option was
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index c7da741284e5..6c051ca6bcf7 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -454,7 +454,7 @@ test_expect_success 'warn on improper hash version' '
 
 test_expect_success 'git commit-graph verify' '
 	cd "$TRASH_DIRECTORY/full" &&
-	git rev-parse commits/8 | GIT_TEST_COMMIT_GRAPH_NO_GDAT=1 git commit-graph write --stdin-commits &&
+	git rev-parse commits/8 | git -c commitGraph.generationVersion=1 commit-graph write --stdin-commits &&
 	git commit-graph verify >output &&
 	graph_read_expect 9 extra_edges
 '
diff --git a/t/t5324-split-commit-graph.sh b/t/t5324-split-commit-graph.sh
index 8e90f3423b8f..587226ed1032 100755
--- a/t/t5324-split-commit-graph.sh
+++ b/t/t5324-split-commit-graph.sh
@@ -489,7 +489,7 @@ test_expect_success 'setup repo for mixed generation commit-graph-chain' '
 			test_commit $i &&
 			git branch commits/$i || return 1
 		done &&
-		git commit-graph write --reachable --split &&
+		git -c commitGraph.generationVersion=2 commit-graph write --reachable --split &&
 		graph_read_expect $NUM_FIRST_LAYER_COMMITS &&
 		test_line_count = 1 $graphdir/commit-graph-chain &&
 		for i in $(test_seq $SECOND_LAYER_SEQUENCE_START $SECOND_LAYER_SEQUENCE_END)
@@ -497,7 +497,7 @@ test_expect_success 'setup repo for mixed generation commit-graph-chain' '
 			test_commit $i &&
 			git branch commits/$i || return 1
 		done &&
-		GIT_TEST_COMMIT_GRAPH_NO_GDAT=1 git commit-graph write --reachable --split=no-merge &&
+		git -c commitGraph.generationVersion=1 commit-graph write --reachable --split=no-merge &&
 		test_line_count = 2 $graphdir/commit-graph-chain &&
 		test-tool read-graph >output &&
 		cat >expect <<-EOF &&
diff --git a/t/t6600-test-reach.sh b/t/t6600-test-reach.sh
index e2d33a8a4c46..3d7a62ddab61 100755
--- a/t/t6600-test-reach.sh
+++ b/t/t6600-test-reach.sh
@@ -55,7 +55,7 @@ test_expect_success 'setup' '
 	git show-ref -s commit-5-5 | git commit-graph write --stdin-commits &&
 	mv .git/objects/info/commit-graph commit-graph-half &&
 	chmod u+w commit-graph-half &&
-	GIT_TEST_COMMIT_GRAPH_NO_GDAT=1 git commit-graph write --reachable &&
+	git -c commitGraph.generationVersion=1 commit-graph write --reachable &&
 	mv .git/objects/info/commit-graph commit-graph-no-gdat &&
 	chmod u+w commit-graph-no-gdat &&
 	git config core.commitGraph true
-- 
gitgitgadget