commit: add a commit.verbose config variable

Add commit.verbose configuration variable as a convenience for those
who always prefer --verbose.

Add tests to check the behavior introduced by this commit and also to
verify that behavior of status doesn't break because of this commit.

Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/commit.c b/builtin/commit.c
index 98e1527..a486620 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -114,6 +114,7 @@
 static int all, also, interactive, patch_interactive, only, amend, signoff;
 static int edit_flag = -1; /* unspecified */
 static int quiet, verbose, no_verify, allow_empty, dry_run, renew_authorship;
+static int config_commit_verbose = -1; /* unspecified */
 static int no_post_rewrite, allow_empty_message;
 static char *untracked_files_arg, *force_date, *ignore_submodule_arg;
 static char *sign_commit;
@@ -1515,6 +1516,11 @@
 		sign_commit = git_config_bool(k, v) ? "" : NULL;
 		return 0;
 	}
+	if (!strcmp(k, "commit.verbose")) {
+		int is_bool;
+		config_commit_verbose = git_config_bool_or_int(k, v, &is_bool);
+		return 0;
+	}
 
 	status = git_gpg_config(k, v, NULL);
 	if (status)
@@ -1661,9 +1667,13 @@
 		if (parse_commit(current_head))
 			die(_("could not parse HEAD commit"));
 	}
+	verbose = -1; /* unspecified */
 	argc = parse_and_validate_options(argc, argv, builtin_commit_options,
 					  builtin_commit_usage,
 					  prefix, current_head, &s);
+	if (verbose == -1)
+		verbose = (config_commit_verbose < 0) ? 0 : config_commit_verbose;
+
 	if (dry_run)
 		return dry_run_commit(argc, argv, prefix, current_head, &s);
 	index_file = prepare_index(argc, argv, prefix, current_head, 0);