cat-file: add remote-object-info to batch-command

Since the `info` command in cat-file --batch-command prints object info
for a given object, it is natural to add another command in cat-file
--batch-command to print object info for a given object from a remote.
Add `remote-object-info` to cat-file --batch-command.

While `info` takes object ids one at a time, this creates overhead when
making requests to a server so `remote-object-info` instead can take
multiple object ids at once.

cat-file --batch-command is generally implemented in the following
manner:

 - Receive and parse input from user
 - Call respective function attached to command
 - Get object info, print object info

In --buffer mode, this changes to:

 - Receive and parse input from user
 - Store respective function attached to command in a queue
 - After flush, loop through commands in queue
    - Call respective function attached to command
    - Get object info, print object info

Notice how the getting and printing of object info is accomplished one
at a time. As described above, this creates a problem for making
requests to a server. Therefore, `remote-object-info` is implemented in
the following manner:

 - Receive and parse input from user
 If command is `remote-object-info`:
    - Get object info from remote
    - Loop through and print each object info
 Else:
    - Call respective function attached to command
    - Parse input, get object info, print object info

And finally for --buffer mode `remote-object-info`:
 - Receive and parse input from user
 - Store respective function attached to command in a queue
 - After flush, loop through commands in queue:
    If command is `remote-object-info`:
        - Get object info from remote
        - Loop through and print each object info
    Else:
        - Call respective function attached to command
        - Get object info, print object info

To summarize, `remote-object-info` gets object info from the remote and
then loop through the object info passed in, print the info.

In order for remote-object-info to avoid remote communication overhead
in the non-buffer mode, the objects are passed in as such:

remote-object-info <remote> <oid> <oid> ... <oid>

rather than

remote-object-info <remote> <oid>
remote-object-info <remote> <oid>
...
remote-object-info <remote> <oid>

Helped-by: Jonathan Tan <[email protected]>
Helped-by: Christian Couder <[email protected]>
Signed-off-by: Calvin Wan <[email protected]>
Signed-off-by: Eric Ju  <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Documentation/git-cat-file.txt

@@ -149,6 +149,13 @@ info <object>::
 	Print object info for object reference `<object>`. This corresponds to the
 	output of `--batch-check`.
 
+remote-object-info <remote> <object>...::
+	Print object info for object references `<object>` at specified <remote> without
+	downloading objects from remote. If the object-info capability is not
+	supported by the server, the objects will be downloaded instead.
+	Error when no object references are provided.
+	This command may be combined with `--buffer`.
+
 flush::
 	Used with `--buffer` to execute all preceding commands that were issued
 	since the beginning or since the last flush was issued. When `--buffer`
@@ -290,21 +297,23 @@ newline. The available atoms are:
 	The full hex representation of the object name.
 
 `objecttype`::
-	The type of the object (the same as `cat-file -t` reports).
+	The type of the object (the same as `cat-file -t` reports). See
+	`CAVEATS` below. Not supported by `remote-object-info`.
 
 `objectsize`::
 	The size, in bytes, of the object (the same as `cat-file -s`
 	reports).
 
 `objectsize:disk`::
 	The size, in bytes, that the object takes up on disk. See the
-	note about on-disk sizes in the `CAVEATS` section below.
+	note about on-disk sizes in the `CAVEATS` section below. Not
+	supported by `remote-object-info`.
 
 `deltabase`::
 	If the object is stored as a delta on-disk, this expands to the
 	full hex representation of the delta base object name.
 	Otherwise, expands to the null OID (all zeroes). See `CAVEATS`
-	below.
+	below. Not supported by `remote-object-info`.
 
 `rest`::
 	If this atom is used in the output string, input lines are split
@@ -314,7 +323,9 @@ newline. The available atoms are:
 	line) are output in place of the `%(rest)` atom.
 
 If no format is specified, the default format is `%(objectname)
-%(objecttype) %(objectsize)`.
+%(objecttype) %(objectsize)`, except for `remote-object-info` commands which use
+`%(objectname) %(objectsize)` for now because "%(objecttype)" is not supported yet.
+When "%(objecttype)" is supported, default format should be unified.
 
 If `--batch` is specified, or if `--batch-command` is used with the `contents`
 command, the object information is followed by the object contents (consisting
@@ -396,6 +407,9 @@ scripting purposes.
 CAVEATS
 -------
 
+Note that since %(objecttype), %(objectsize:disk) and %(deltabase) are currently not supported by the
+`remote-object-info` command, we will error and exit when they are in the format string.
+
 Note that the sizes of objects on disk are reported accurately, but care
 should be taken in drawing conclusions about which refs or objects are
 responsible for disk usage. The size of a packed non-delta object may be

builtin/cat-file.c

@@ -24,6 +24,9 @@
 #include "promisor-remote.h"
 #include "mailmap.h"
 #include "write-or-die.h"
+#include "alias.h"
+#include "remote.h"
+#include "transport.h"
 
 enum batch_mode {
 	BATCH_MODE_CONTENTS,
@@ -42,9 +45,12 @@ struct batch_options {
 	char input_delim;
 	char output_delim;
 	const char *format;
+	int use_remote_info;
 };
 
 static const char *force_path;
+static struct object_info *remote_object_info;
+static struct oid_array object_info_oids = OID_ARRAY_INIT;
 
 static struct string_list mailmap = STRING_LIST_INIT_NODUP;
 static int use_mailmap;
@@ -528,7 +534,7 @@ static void batch_one_object(const char *obj_name,
 	enum get_oid_result result;
 
 	result = get_oid_with_context(the_repository, obj_name,
-				      flags, &data->oid, &ctx);
+								  flags, &data->oid, &ctx);
 	if (result != FOUND) {
 		switch (result) {
 		case MISSING_OBJECT:
@@ -576,6 +582,59 @@ static void batch_one_object(const char *obj_name,
 	object_context_release(&ctx);
 }
 
+static int get_remote_info(struct batch_options *opt, int argc, const char **argv)
+{
+	int retval = 0;
+	struct remote *remote = NULL;
+	struct object_id oid;
+	struct string_list object_info_options = STRING_LIST_INIT_NODUP;
+	static struct transport *gtransport;
+
+	/*
+	 * Change the format to "%(objectname) %(objectsize)" when
+	 * remote-object-info command is used. Once we start supporting objecttype
+	 * the default format should change to DEFAULT_FORMAT
+	*/
+	if (!opt->format)
+		opt->format = "%(objectname) %(objectsize)";
+
+	remote = remote_get(argv[0]);
+	if (!remote)
+		die(_("must supply valid remote when using remote-object-info"));
+
+	oid_array_clear(&object_info_oids);
+	for (size_t i = 1; i < argc; i++) {
+		if (get_oid_hex(argv[i], &oid))
+			die(_("Not a valid object name %s"), argv[i]);
+		oid_array_append(&object_info_oids, &oid);
+	}
+
+	gtransport = transport_get(remote, NULL);
+	if (gtransport->smart_options) {
+		CALLOC_ARRAY(remote_object_info, object_info_oids.nr);
+		gtransport->smart_options->object_info = 1;
+		gtransport->smart_options->object_info_oids = &object_info_oids;
+
+		/* 'objectsize' is the only option currently supported */
+		if (!strstr(opt->format, "%(objectsize)"))
+			die(_("%s is currently not supported with remote-object-info"), opt->format);
+
+		string_list_append(&object_info_options, "size");
+
+		if (object_info_options.nr > 0) {
+			gtransport->smart_options->object_info_options = &object_info_options;
+			gtransport->smart_options->object_info_data = remote_object_info;
+			retval = transport_fetch_refs(gtransport, NULL);
+		}
+	} else {
+		retval = -1;
+	}
+
+	string_list_clear(&object_info_options, 0);
+	transport_disconnect(gtransport);
+	return retval;
+}
+
 struct object_cb_data {
 	struct batch_options *opt;
 	struct expand_data *expand;
@@ -667,6 +726,52 @@ static void parse_cmd_info(struct batch_options *opt,
 	batch_one_object(line, output, opt, data);
 }
 
+static void parse_cmd_remote_object_info(struct batch_options *opt,
+			   const char *line,
+			   struct strbuf *output,
+			   struct expand_data *data)
+{
+	int count;
+	const char **argv;
+
+	char *line_to_split = xstrdup_or_null(line);
+	count = split_cmdline(line_to_split, &argv);
+	if (get_remote_info(opt, count, argv))
+		goto cleanup;
+
+	opt->use_remote_info = 1;
+	data->skip_object_info = 1;
+	for (size_t i = 0; i < object_info_oids.nr; i++) {
+
+		data->oid = object_info_oids.oid[i];
+
+		if (remote_object_info[i].sizep) {
+			data->size = *remote_object_info[i].sizep;
+		} else {
+			/*
+			 * When reaching here, it means remote-object-info can't retrieve
+			 * information from server without downloading them, and the objects
+			 * have been fetched to client already.
+			 * Print the information using the logic for local objects.
+			 */
+			data->skip_object_info = 0;
+		}
+
+		opt->batch_mode = BATCH_MODE_INFO;
+		batch_object_write(argv[i+1], output, opt, data, NULL, 0);
+
+	}
+	opt->use_remote_info = 0;
+	data->skip_object_info = 0;
+
+cleanup:
+	for (size_t i = 0; i < object_info_oids.nr; i++)
+		free_object_info_contents(&remote_object_info[i]);
+	free(line_to_split);
+	free(argv);
+	free(remote_object_info);
+}
+
 static void dispatch_calls(struct batch_options *opt,
 		struct strbuf *output,
 		struct expand_data *data,
@@ -698,6 +803,7 @@ static const struct parse_cmd {
 } commands[] = {
 	{ "contents", parse_cmd_contents, 1},
 	{ "info", parse_cmd_info, 1},
+	{ "remote-object-info", parse_cmd_remote_object_info, 1},
 	{ "flush", NULL, 0},
 };
 

object-file.c

@@ -3020,3 +3020,14 @@ int read_loose_object(const char *path,
 		munmap(map, mapsize);
 	return ret;
 }
+
+void free_object_info_contents(struct object_info *object_info)
+{
+	if (!object_info)
+		return;
+	free(object_info->typep);
+	free(object_info->sizep);
+	free(object_info->disk_sizep);
+	free(object_info->delta_base_oid);
+	free(object_info->type_name);
+}

object-store-ll.h

@@ -548,4 +548,7 @@ int for_each_object_in_pack(struct packed_git *p,
 int for_each_packed_object(each_packed_object_fn, void *,
 			   enum for_each_object_flags flags);
 
+/* Free pointers inside of object_info, but not object_info itself */
+void free_object_info_contents(struct object_info *object_info);
+
 #endif /* OBJECT_STORE_LL_H */