[PATCH 8/8] archive: support creating archives from index

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

This is more or less for fun. Does anyone really want to create archives
from index?

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 archive.c |   38 +++++++++++++++++++++++++-------------
 archive.h |    1 +
 2 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/archive.c b/archive.c
index 1ce644e..bb0a0f1 100644
--- a/archive.c
+++ b/archive.c
@@ -181,7 +181,7 @@ int write_archive_entries(struct archiver_args *args,
 			len--;
 		if (args->verbose)
 			fprintf(stderr, "%.*s\n", (int)len, args->base);
-		err = write_entry(args, args->tree->object.sha1, args->base,
+		err = write_entry(args, args->tree ? args->tree->object.sha1 : null_sha1, args->base,
 				len, 040777, NULL, 0);
 		if (err)
 			return err;
@@ -190,15 +190,19 @@ int write_archive_entries(struct archiver_args *args,
 	context.args = args;
 	context.write_entry = write_entry;
 
-	memset(&opts, 0, sizeof(opts));
-	opts.index_only = 1;
-	opts.head_idx = -1;
-	opts.src_index = &the_index;
-	opts.dst_index = &the_index;
-	opts.fn = oneway_merge;
-	init_tree_desc(&t, args->tree->buffer, args->tree->size);
-	if (unpack_trees(1, &t, &opts))
-		return -1;
+	if (args->tree) {
+		memset(&opts, 0, sizeof(opts));
+		opts.index_only = 1;
+		opts.head_idx = -1;
+		opts.src_index = &the_index;
+		opts.dst_index = &the_index;
+		opts.fn = oneway_merge;
+		init_tree_desc(&t, args->tree->buffer, args->tree->size);
+		if (unpack_trees(1, &t, &opts))
+			return -1;
+	}
+	else
+		read_cache();
 	prefix_len = common_prefix(args->pathspec);
 	if (prefix_len)
 		prune_cache(args->pathspec[0], prefix_len);
@@ -300,6 +304,7 @@ static int parse_archive_args(int argc, const char **argv,
 	int verbose = 0;
 	int i;
 	int list = 0;
+	int use_index = 0;
 	struct option opts[] = {
 		OPT_GROUP(""),
 		OPT_STRING('f', "format", &format, "fmt", "archive format"),
@@ -307,6 +312,8 @@ static int parse_archive_args(int argc, const char **argv,
 			"prepend prefix to each pathname in the archive"),
 		OPT_STRING(0, "output", &output, "file",
 			"write the archive to this file"),
+		OPT_BOOLEAN('i', "index", &use_index,
+			"generate from index instead"),
 		OPT__VERBOSE(&verbose),
 		OPT__COMPR('0', &compression_level, "store only", 0),
 		OPT__COMPR('1', &compression_level, "compress faster", 1),
@@ -348,7 +355,7 @@ static int parse_archive_args(int argc, const char **argv,
 	}
 
 	/* We need at least one parameter -- tree-ish */
-	if (argc < 1)
+	if (argc < 1 && !use_index)
 		usage_with_options(archive_usage, opts);
 	*ar = lookup_archiver(format);
 	if (!*ar)
@@ -366,6 +373,7 @@ static int parse_archive_args(int argc, const char **argv,
 	args->verbose = verbose;
 	args->base = base;
 	args->baselen = strlen(base);
+	args->use_index = use_index;
 
 	return argc;
 }
@@ -376,12 +384,16 @@ int write_archive(int argc, const char **argv, const char *prefix,
 	const struct archiver *ar = NULL;
 	struct archiver_args args;
 
+	memset(&args, 0, sizeof(args));
 	argc = parse_archive_args(argc, argv, &ar, &args);
 	if (setup_prefix && prefix == NULL)
 		prefix = setup_git_directory();
 
-	parse_treeish_arg(argv, &args, prefix);
-	parse_pathspec_arg(argv + 1, &args, prefix);
+	if (!args.use_index) {
+		parse_treeish_arg(argv, &args, prefix);
+		argv++;
+	}
+	parse_pathspec_arg(argv, &args, prefix);
 
 	git_config(git_default_config, NULL);
 
diff --git a/archive.h b/archive.h
index 0b15b35..fb94d47 100644
--- a/archive.h
+++ b/archive.h
@@ -10,6 +10,7 @@ struct archiver_args {
 	time_t time;
 	const char **pathspec;
 	unsigned int verbose : 1;
+	unsigned int use_index : 1;
 	int compression_level;
 };
 
-- 
1.6.2.2.602.g83ee9f