[PATCH 03/14] packed-graph: create git-graph builtin

[Derrick Stolee <stolee@gmail.com>]

Teach Git the 'graph' builtin that will be used for writing and
reading packed graph files. The current implementation is mostly
empty, except for a check that the core.graph setting is enabled
and a '--pack-dir' option.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Documentation/git-graph.txt |  7 +++++++
 Makefile                    |  1 +
 builtin.h                   |  1 +
 builtin/graph.c             | 36 ++++++++++++++++++++++++++++++++++++
 command-list.txt            |  1 +
 git.c                       |  1 +
 6 files changed, 47 insertions(+)
 create mode 100644 Documentation/git-graph.txt
 create mode 100644 builtin/graph.c

diff --git a/Documentation/git-graph.txt b/Documentation/git-graph.txt
new file mode 100644
index 0000000000..de5a3c07e6
--- /dev/null
+++ b/Documentation/git-graph.txt
@@ -0,0 +1,7 @@
+git-graph(1)
+============
+
+NAME
+----
+git-graph - Write and verify Git commit graphs (.graph files)
+
diff --git a/Makefile b/Makefile
index 1a9b23b679..d8b0d0457a 100644
--- a/Makefile
+++ b/Makefile
@@ -965,6 +965,7 @@ BUILTIN_OBJS += builtin/for-each-ref.o
 BUILTIN_OBJS += builtin/fsck.o
 BUILTIN_OBJS += builtin/gc.o
 BUILTIN_OBJS += builtin/get-tar-commit-id.o
+BUILTIN_OBJS += builtin/graph.o
 BUILTIN_OBJS += builtin/grep.o
 BUILTIN_OBJS += builtin/hash-object.o
 BUILTIN_OBJS += builtin/help.o
diff --git a/builtin.h b/builtin.h
index 42378f3aa4..ae7e816908 100644
--- a/builtin.h
+++ b/builtin.h
@@ -168,6 +168,7 @@ extern int cmd_format_patch(int argc, const char **argv, const char *prefix);
 extern int cmd_fsck(int argc, const char **argv, const char *prefix);
 extern int cmd_gc(int argc, const char **argv, const char *prefix);
 extern int cmd_get_tar_commit_id(int argc, const char **argv, const char *prefix);
+extern int cmd_graph(int argc, const char **argv, const char *prefix);
 extern int cmd_grep(int argc, const char **argv, const char *prefix);
 extern int cmd_hash_object(int argc, const char **argv, const char *prefix);
 extern int cmd_help(int argc, const char **argv, const char *prefix);
diff --git a/builtin/graph.c b/builtin/graph.c
new file mode 100644
index 0000000000..a902dc8646
--- /dev/null
+++ b/builtin/graph.c
@@ -0,0 +1,36 @@
+#include "builtin.h"
+#include "cache.h"
+#include "config.h"
+#include "dir.h"
+#include "git-compat-util.h"
+#include "lockfile.h"
+#include "packfile.h"
+#include "parse-options.h"
+
+static char const * const builtin_graph_usage[] ={
+	N_("git graph [--pack-dir <packdir>]"),
+	NULL
+};
+
+static struct opts_graph {
+	const char *pack_dir;
+} opts;
+
+int cmd_graph(int argc, const char **argv, const char *prefix)
+{
+	static struct option builtin_graph_options[] = {
+		{ OPTION_STRING, 'p', "pack-dir", &opts.pack_dir,
+			N_("dir"),
+			N_("The pack directory to store the graph") },
+		OPT_END(),
+	};
+
+	if (!core_graph)
+		die("core.graph is false");
+
+	if (argc == 2 && !strcmp(argv[1], "-h"))
+		usage_with_options(builtin_graph_usage, builtin_graph_options);
+
+	return 0;
+}
+
diff --git a/command-list.txt b/command-list.txt
index a1fad28fd8..d9c17cb9f8 100644
--- a/command-list.txt
+++ b/command-list.txt
@@ -61,6 +61,7 @@ git-format-patch                        mainporcelain
 git-fsck                                ancillaryinterrogators
 git-gc                                  mainporcelain
 git-get-tar-commit-id                   ancillaryinterrogators
+git-graph                               plumbingmanipulators
 git-grep                                mainporcelain           info
 git-gui                                 mainporcelain
 git-hash-object                         plumbingmanipulators
diff --git a/git.c b/git.c
index c870b9719c..29f8b6e7dd 100644
--- a/git.c
+++ b/git.c
@@ -408,6 +408,7 @@ static struct cmd_struct commands[] = {
 	{ "fsck-objects", cmd_fsck, RUN_SETUP },
 	{ "gc", cmd_gc, RUN_SETUP },
 	{ "get-tar-commit-id", cmd_get_tar_commit_id },
+	{ "graph", cmd_graph, RUN_SETUP_GENTLY },
 	{ "grep", cmd_grep, RUN_SETUP_GENTLY },
 	{ "hash-object", cmd_hash_object },
 	{ "help", cmd_help },
-- 
2.16.0