[PATCH v3 04/24] multi-pack-index: add 'write' verb

[Derrick Stolee <stolee@gmail.com>]

In anticipation of writing multi-pack-indexes, add a
'git multi-pack-index write' subcommand and send the options to a
write_midx_file() method. Also create a basic test file that tests
the 'write' subcommand.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Documentation/git-multi-pack-index.txt | 22 +++++++++++++++++++++-
 Makefile                               |  1 +
 builtin/multi-pack-index.c             | 10 +++++++++-
 midx.c                                 |  7 +++++++
 midx.h                                 |  6 ++++++
 t/t5319-multi-pack-index.sh            | 10 ++++++++++
 6 files changed, 54 insertions(+), 2 deletions(-)
 create mode 100644 midx.c
 create mode 100644 midx.h
 create mode 100755 t/t5319-multi-pack-index.sh

diff --git a/Documentation/git-multi-pack-index.txt b/Documentation/git-multi-pack-index.txt
index a83c0496a6..be97c9372e 100644
--- a/Documentation/git-multi-pack-index.txt
+++ b/Documentation/git-multi-pack-index.txt
@@ -9,7 +9,7 @@ git-multi-pack-index - Write and verify multi-pack-indexes
 SYNOPSIS
 --------
 [verse]
-'git multi-pack-index' [--object-dir <dir>]
+'git multi-pack-index' [--object-dir <dir>] <verb>
 
 DESCRIPTION
 -----------
@@ -23,6 +23,26 @@ OPTIONS
 	`<dir>/packs/multi-pack-index` for the current MIDX file, and
 	`<dir>/packs` for the pack-files to index.
 
+write::
+	When given as the verb, write a new MIDX file to
+	`<dir>/packs/multi-pack-index`.
+
+
+EXAMPLES
+--------
+
+* Write a MIDX file for the packfiles in the current .git folder.
++
+-----------------------------------------------
+$ git multi-pack-index write
+-----------------------------------------------
+
+* Write a MIDX file for the packfiles in an alternate.
++
+-----------------------------------------------
+$ git multi-pack-index --object-dir <alt> write
+-----------------------------------------------
+
 
 SEE ALSO
 --------
diff --git a/Makefile b/Makefile
index 54610875ec..f5636c711d 100644
--- a/Makefile
+++ b/Makefile
@@ -890,6 +890,7 @@ LIB_OBJS += merge.o
 LIB_OBJS += merge-blobs.o
 LIB_OBJS += merge-recursive.o
 LIB_OBJS += mergesort.o
+LIB_OBJS += midx.o
 LIB_OBJS += name-hash.o
 LIB_OBJS += notes.o
 LIB_OBJS += notes-cache.o
diff --git a/builtin/multi-pack-index.c b/builtin/multi-pack-index.c
index 4853291477..14b32e1373 100644
--- a/builtin/multi-pack-index.c
+++ b/builtin/multi-pack-index.c
@@ -2,9 +2,10 @@
 #include "cache.h"
 #include "config.h"
 #include "parse-options.h"
+#include "midx.h"
 
 static char const * const builtin_multi_pack_index_usage[] = {
-	N_("git multi-pack-index [--object-dir <dir>]"),
+	N_("git multi-pack-index [--object-dir <dir>] [write]"),
 	NULL
 };
 
@@ -34,5 +35,12 @@ int cmd_multi_pack_index(int argc, const char **argv,
 	if (!opts.object_dir)
 		opts.object_dir = get_object_directory();
 
+	if (argc == 0)
+		usage_with_options(builtin_multi_pack_index_usage,
+				   builtin_multi_pack_index_options);
+
+	if (!strcmp(argv[0], "write"))
+		return write_midx_file(opts.object_dir);
+
 	return 0;
 }
diff --git a/midx.c b/midx.c
new file mode 100644
index 0000000000..32468db1a2
--- /dev/null
+++ b/midx.c
@@ -0,0 +1,7 @@
+#include "cache.h"
+#include "midx.h"
+
+int write_midx_file(const char *object_dir)
+{
+	return 0;
+}
diff --git a/midx.h b/midx.h
new file mode 100644
index 0000000000..dbdbe9f873
--- /dev/null
+++ b/midx.h
@@ -0,0 +1,6 @@
+#ifndef __MIDX_H__
+#define __MIDX_H__
+
+int write_midx_file(const char *object_dir);
+
+#endif
diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
new file mode 100755
index 0000000000..ec3ddbe79c
--- /dev/null
+++ b/t/t5319-multi-pack-index.sh
@@ -0,0 +1,10 @@
+#!/bin/sh
+
+test_description='multi-pack-indexes'
+. ./test-lib.sh
+
+test_expect_success 'write midx with no packs' '
+	git multi-pack-index --object-dir=. write
+'
+
+test_done
-- 
2.18.0.118.gd4f65b8d14