Merge branch 'jk/info-alternates-fix' into maint

We used to add an empty alternate object database to the system
that does not help anything; it has been corrected.

* jk/info-alternates-fix:
  link_alt_odb_entries: make empty input a noop

Author: gitster

sha1_file.c

@@ -404,6 +404,9 @@ static void link_alt_odb_entries(const char *alt, int sep,
 	struct strbuf objdirbuf = STRBUF_INIT;
 	struct strbuf entry = STRBUF_INIT;
 
+	if (!alt || !*alt)
+		return;
+
 	if (depth > 5) {
 		error("%s: ignoring alternate object stores, nesting too deep.",
 				relative_base);
@@ -607,7 +610,6 @@ void prepare_alt_odb(void)
 		return;
 
 	alt = getenv(ALTERNATE_DB_ENVIRONMENT);
-	if (!alt) alt = "";
 
 	alt_odb_tail = &alt_odb_list;
 	link_alt_odb_entries(alt, PATH_SEP, NULL, 0);