send-email: allow use of aliases in the From field of --compose mode

Aliases were expanded before considering the From field of the
--compose option. This is inconsistent with other fields
(To, Cc, ...) which already support aliases.

Signed-off-by: Remi Lespinet <remi.lespinet@ensimag.grenoble-inp.fr>
Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-send-email.perl

@@ -530,8 +530,6 @@ if (@alias_files and $aliasfiletype and defined $parse_alias{$aliasfiletype}) {
 	}
 }
 
-($sender) = expand_aliases($sender) if defined $sender;
-
 # is_format_patch_arg($f) returns 0 if $f names a patch, or 1 if
 # $f is a revision list specification to be passed to format-patch.
 sub is_format_patch_arg {
@@ -776,6 +774,8 @@ if (!$force) {
 	}
 }
 
+($sender) = expand_aliases($sender) if defined $sender;
+
 if (!defined $sender) {
 	$sender = $repoauthor || $repocommitter || '';
 }