config: initialize opts structure in repo_read_config()

Initialize opts structure in repo_read_config().

This change fixes a crash in later commit after a new field is added
to the structure.

In commit 3b256228a6, repo_read_config()
was added.  It only initializes 3 fields in the opts structure.  It is
passed to config_with_options() and then to do_git_config_sequence().
However, do_git_config_sequence() drops the opts on the floor and calls
git_config_from_file() rather than git_config_from_file_with_options(),
so that may be why this hasn't been a problem in the past.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

config.c

@@ -2011,7 +2011,7 @@ int git_configset_get_pathname(struct config_set *cs, const char *key, const cha
 /* Functions use to read configuration from a repository */
 static void repo_read_config(struct repository *repo)
 {
-	struct config_options opts;
+	struct config_options opts = { 0 };
 
 	opts.respect_includes = 1;
 	opts.commondir = repo->commondir;