Merge branch 'nd/error-errno'

The code for warning_errno/die_errno has been refactored and a new
error_errno() reporting helper is introduced.

* nd/error-errno: (41 commits)
  wrapper.c: use warning_errno()
  vcs-svn: use error_errno()
  upload-pack.c: use error_errno()
  unpack-trees.c: use error_errno()
  transport-helper.c: use error_errno()
  sha1_file.c: use {error,die,warning}_errno()
  server-info.c: use error_errno()
  sequencer.c: use error_errno()
  run-command.c: use error_errno()
  rerere.c: use error_errno() and warning_errno()
  reachable.c: use error_errno()
  mailmap.c: use error_errno()
  ident.c: use warning_errno()
  http.c: use error_errno() and warning_errno()
  grep.c: use error_errno()
  gpg-interface.c: use error_errno()
  fast-import.c: use error_errno()
  entry.c: use error_errno()
  editor.c: use error_errno()
  diff-no-index.c: use error_errno()
  ...

mailmap.c

@@ -189,8 +189,7 @@ static int read_mailmap_file(struct string_list *map, const char *filename,
 	if (!f) {
 		if (errno == ENOENT)
 			return 0;
-		return error("unable to open mailmap at %s: %s",
-			     filename, strerror(errno));
+		return error_errno("unable to open mailmap at %s", filename);
 	}
 
 	while (fgets(buffer, sizeof(buffer), f) != NULL)