commit-graph: add --split option to builtin

Add a new "--split" option to the 'git commit-graph write' subcommand. This
option allows the optional behavior of writing a commit-graph chain.

The current behavior will add a tip commit-graph containing any commits that
are not in the existing commit-graph or commit-graph chain. Later changes
will allow merging the chain and expiring out-dated files.

Add a new test script (t5324-split-commit-graph.sh) that demonstrates this
behavior.

Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
index d8efa5bab27..ff8bc3c8b9e 100644
--- a/builtin/commit-graph.c
+++ b/builtin/commit-graph.c
@@ -10,7 +10,7 @@ static char const * const builtin_commit_graph_usage[] = {
 	N_("git commit-graph [--object-dir <objdir>]"),
 	N_("git commit-graph read [--object-dir <objdir>]"),
 	N_("git commit-graph verify [--object-dir <objdir>]"),
-	N_("git commit-graph write [--object-dir <objdir>] [--append] [--reachable|--stdin-packs|--stdin-commits]"),
+	N_("git commit-graph write [--object-dir <objdir>] [--append|--split] [--reachable|--stdin-packs|--stdin-commits]"),
 	NULL
 };
 
@@ -25,7 +25,7 @@ static const char * const builtin_commit_graph_read_usage[] = {
 };
 
 static const char * const builtin_commit_graph_write_usage[] = {
-	N_("git commit-graph write [--object-dir <objdir>] [--append] [--reachable|--stdin-packs|--stdin-commits]"),
+	N_("git commit-graph write [--object-dir <objdir>] [--append|--split] [--reachable|--stdin-packs|--stdin-commits]"),
 	NULL
 };
 
@@ -35,9 +35,9 @@ static struct opts_commit_graph {
 	int stdin_packs;
 	int stdin_commits;
 	int append;
+	int split;
 } opts;
 
-
 static int graph_verify(int argc, const char **argv)
 {
 	struct commit_graph *graph = NULL;
@@ -156,6 +156,8 @@ static int graph_write(int argc, const char **argv)
 			N_("start walk at commits listed by stdin")),
 		OPT_BOOL(0, "append", &opts.append,
 			N_("include all commits already in the commit-graph file")),
+		OPT_BOOL(0, "split", &opts.split,
+			N_("allow writing an incremental commit-graph file")),
 		OPT_END(),
 	};
 
@@ -169,6 +171,8 @@ static int graph_write(int argc, const char **argv)
 		opts.obj_dir = get_object_directory();
 	if (opts.append)
 		flags |= COMMIT_GRAPH_APPEND;
+	if (opts.split)
+		flags |= COMMIT_GRAPH_SPLIT;
 
 	read_replace_refs = 0;