fetch-pack: use argv_array for index-pack / unpack-objects

This cleans up a magic number that must be kept in sync with
the rest of the code (the number of argv slots). It also
lets us drop some fixed buffers and an sprintf (since we
can now use argv_array_pushf).

We do still have to keep one fixed buffer for calling
gethostname, but at least now the size computations for it
are much simpler.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

fetch-pack.c

@@ -681,11 +681,10 @@ static int get_pack(struct fetch_pack_args *args,
 		    int xd[2], char **pack_lockfile)
 {
 	struct async demux;
-	const char *argv[22];
-	char keep_arg[256];
-	char hdr_arg[256];
-	const char **av, *cmd_name;
 	int do_keep = args->keep_pack;
+	const char *cmd_name;
+	struct pack_header header;
+	int pass_header = 0;
 	struct child_process cmd = CHILD_PROCESS_INIT;
 	int ret;
 
@@ -705,17 +704,11 @@ static int get_pack(struct fetch_pack_args *args,
 	else
 		demux.out = xd[0];
 
-	cmd.argv = argv;
-	av = argv;
-	*hdr_arg = 0;
 	if (!args->keep_pack && unpack_limit) {
-		struct pack_header header;
 
 		if (read_pack_header(demux.out, &header))
 			die("protocol error: bad pack header");
-		snprintf(hdr_arg, sizeof(hdr_arg),
-			 "--pack_header=%"PRIu32",%"PRIu32,
-			 ntohl(header.hdr_version), ntohl(header.hdr_entries));
+		pass_header = 1;
 		if (ntohl(header.hdr_entries) < unpack_limit)
 			do_keep = 0;
 		else
@@ -723,44 +716,49 @@ static int get_pack(struct fetch_pack_args *args,
 	}
 
 	if (alternate_shallow_file) {
-		*av++ = "--shallow-file";
-		*av++ = alternate_shallow_file;
+		argv_array_push(&cmd.args, "--shallow-file");
+		argv_array_push(&cmd.args, alternate_shallow_file);
 	}
 
 	if (do_keep) {
 		if (pack_lockfile)
 			cmd.out = -1;
-		*av++ = cmd_name = "index-pack";
-		*av++ = "--stdin";
+		cmd_name = "index-pack";
+		argv_array_push(&cmd.args, cmd_name);
+		argv_array_push(&cmd.args, "--stdin");
 		if (!args->quiet && !args->no_progress)
-			*av++ = "-v";
+			argv_array_push(&cmd.args, "-v");
 		if (args->use_thin_pack)
-			*av++ = "--fix-thin";
+			argv_array_push(&cmd.args, "--fix-thin");
 		if (args->lock_pack || unpack_limit) {
-			int s = sprintf(keep_arg,
-					"--keep=fetch-pack %"PRIuMAX " on ", (uintmax_t) getpid());
-			if (gethostname(keep_arg + s, sizeof(keep_arg) - s))
-				strcpy(keep_arg + s, "localhost");
-			*av++ = keep_arg;
+			char hostname[256];
+			if (gethostname(hostname, sizeof(hostname)))
+				xsnprintf(hostname, sizeof(hostname), "localhost");
+			argv_array_pushf(&cmd.args,
+					"--keep=fetch-pack %"PRIuMAX " on %s",
+					(uintmax_t)getpid(), hostname);
 		}
 		if (args->check_self_contained_and_connected)
-			*av++ = "--check-self-contained-and-connected";
+			argv_array_push(&cmd.args, "--check-self-contained-and-connected");
 	}
 	else {
-		*av++ = cmd_name = "unpack-objects";
+		cmd_name = "unpack-objects";
+		argv_array_push(&cmd.args, cmd_name);
 		if (args->quiet || args->no_progress)
-			*av++ = "-q";
+			argv_array_push(&cmd.args, "-q");
 		args->check_self_contained_and_connected = 0;
 	}
-	if (*hdr_arg)
-		*av++ = hdr_arg;
+
+	if (pass_header)
+		argv_array_pushf(&cmd.args, "--pack_header=%"PRIu32",%"PRIu32,
+				 ntohl(header.hdr_version),
+				 ntohl(header.hdr_entries));
 	if (fetch_fsck_objects >= 0
 	    ? fetch_fsck_objects
 	    : transfer_fsck_objects >= 0
 	    ? transfer_fsck_objects
 	    : 0)
-		*av++ = "--strict";
-	*av++ = NULL;
+		argv_array_push(&cmd.args, "--strict");
 
 	cmd.in = demux.out;
 	cmd.git_cmd = 1;