builtin/fmt-merge-msg: stop depending on 'the_repository'

Refactor builtin/fmt-merge-msg.c to remove the dependancy on the global
'the_repository'. Remove the 'UNUSED' macro from the 'struct repository'
parameter and replace 'git_config()' with 'repo_config()' so that
configuration is read from the passed repository. Also, add a test to
make sure that "git fmt-merge-msg -h" can be called outside a
repository.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Ghanshyam Thakkar <shyamthakkar001@gmail.com>
Signed-off-by: Ayush Chandekar <ayu.chandekar@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: ayu-ch

builtin/fmt-merge-msg.c

@@ -1,4 +1,3 @@
-#define USE_THE_REPOSITORY_VARIABLE
 #include "builtin.h"
 #include "config.h"
 #include "fmt-merge-msg.h"
@@ -13,7 +12,7 @@ static const char * const fmt_merge_msg_usage[] = {
 int cmd_fmt_merge_msg(int argc,
 		      const char **argv,
 		      const char *prefix,
-		      struct repository *repo UNUSED)
+		      struct repository *repo)
 {
 	char *inpath = NULL;
 	const char *message = NULL;
@@ -54,7 +53,7 @@ int cmd_fmt_merge_msg(int argc,
 	int ret;
 	struct fmt_merge_msg_opts opts;
 
-	git_config(fmt_merge_msg_config, &merge_log_config);
+	repo_config(repo, fmt_merge_msg_config, &merge_log_config);
 	argc = parse_options(argc, argv, prefix, options, fmt_merge_msg_usage,
 			     0);
 	if (argc > 0)

t/t1517-outside-repo.sh

@@ -114,4 +114,11 @@ test_expect_success 'update-server-info does not crash with -h' '
 	test_grep "[Uu]sage: git update-server-info " usage
 '
 
+test_expect_success 'fmt-merge-msg does not crash with -h' '
+	test_expect_code 129 git fmt-merge-msg -h >usage &&
+	test_grep "[Uu]sage: git fmt-merge-msg " usage &&
+	test_expect_code 129 nongit git fmt-merge-msg -h >usage &&
+	test_grep "[Uu]sage: git fmt-merge-msg " usage
+'
+
 test_done