fetch.fsckobjects: verify downloaded objects

This corresponds to receive.fsckobjects configuration variable added (a
lot) earlier in 20dc001 (receive-pack: allow using --strict mode for
unpacking objects, 2008-02-25).

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -820,6 +820,12 @@ diff.wordRegex::
 	sequences that match the regular expression are "words", all other
 	characters are *ignorable* whitespace.
 
+fetch.fsckObjects::
+	If it is set to true, git-fetch-pack will check all fetched
+	objects. It will abort in the case of a malformed object or a
+	broken link. The result of an abort are only dangling objects.
+	Defaults to false.
+
 fetch.unpackLimit::
 	If the number of objects fetched over the git native
 	transfer is below this

builtin/fetch-pack.c

@@ -14,6 +14,7 @@ static int transfer_unpack_limit = -1;
 static int fetch_unpack_limit = -1;
 static int unpack_limit = 100;
 static int prefer_ofs_delta = 1;
+static int fetch_fsck_objects;
 static struct fetch_pack_args args = {
 	/* .uploadpack = */ "git-upload-pack",
 };
@@ -663,6 +664,8 @@ static int get_pack(int xd[2], char **pack_lockfile)
 	}
 	if (*hdr_arg)
 		*av++ = hdr_arg;
+	if (fetch_fsck_objects)
+		*av++ = "--strict";
 	*av++ = NULL;
 
 	cmd.in = demux.out;
@@ -776,6 +779,11 @@ static int fetch_pack_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
+	if (!strcmp(var, "fetch.fsckobjects")) {
+		fetch_fsck_objects = git_config_bool(var, value);
+		return 0;
+	}
+
 	return git_default_config(var, value, cb);
 }