Convert existing die(..., strerror(errno)) to die_errno()

Change calls to die(..., strerror(errno)) to use the new die_errno().

In the process, also make slight style adjustments: at least state
_something_ about the function that failed (instead of just printing
the pathname), and put paths in single quotes.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin-config.c b/builtin-config.c
index 60915f9..a2d656e 100644
--- a/builtin-config.c
+++ b/builtin-config.c
@@ -383,8 +383,8 @@
 		check_argc(argc, 0, 0);
 		if (git_config(show_all_config, NULL) < 0) {
 			if (config_exclusive_filename)
-				die("unable to read config file %s: %s",
-				    config_exclusive_filename, strerror(errno));
+				die_errno("unable to read config file '%s'",
+					  config_exclusive_filename);
 			else
 				die("error processing config file(s)");
 		}