send-email: detect invocation errors earlier

We never even look at the command line arguments until after
we have prompted the user for some information. So running
"git send-email" without arguments would prompt for "from"
and "to" headers, only to then die with "No patch files
specified." Instead, let's try to do as much error checking
as possible before getting user input.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-send-email.perl

@@ -314,6 +314,33 @@ if (@alias_files and $aliasfiletype and defined $parse_alias{$aliasfiletype}) {
 
 ($sender) = expand_aliases($sender) if defined $sender;
 
+# Now that all the defaults are set, process the rest of the command line
+# arguments and collect up the files that need to be processed.
+for my $f (@ARGV) {
+	if (-d $f) {
+		opendir(DH,$f)
+			or die "Failed to opendir $f: $!";
+
+		push @files, grep { -f $_ } map { +$f . "/" . $_ }
+				sort readdir(DH);
+
+	} elsif (-f $f) {
+		push @files, $f;
+
+	} else {
+		print STDERR "Skipping $f - not found.\n";
+	}
+}
+
+if (@files) {
+	unless ($quiet) {
+		print $_,"\n" for (@files);
+	}
+} else {
+	print STDERR "\nNo patch files specified!\n\n";
+	usage();
+}
+
 my $prompting = 0;
 if (!defined $sender) {
 	$sender = $repoauthor || $repocommitter;
@@ -427,34 +454,6 @@ EOT
 	@files = ($compose_filename . ".final");
 }
 
-
-# Now that all the defaults are set, process the rest of the command line
-# arguments and collect up the files that need to be processed.
-for my $f (@ARGV) {
-	if (-d $f) {
-		opendir(DH,$f)
-			or die "Failed to opendir $f: $!";
-
-		push @files, grep { -f $_ } map { +$f . "/" . $_ }
-				sort readdir(DH);
-
-	} elsif (-f $f) {
-		push @files, $f;
-
-	} else {
-		print STDERR "Skipping $f - not found.\n";
-	}
-}
-
-if (@files) {
-	unless ($quiet) {
-		print $_,"\n" for (@files);
-	}
-} else {
-	print STDERR "\nNo patch files specified!\n\n";
-	usage();
-}
-
 # Variables we set as part of the loop over files
 our ($message_id, %mail, $subject, $reply_to, $references, $message);