git-notify: Optionally call mail(1) without "-a"

Not all mail(1) implementations support specifying additional header
fields via "-a": with some, this flag is used for attaching files,
others don't provide an "-a" flag at all (this is true for the /bin/mail
utility currently installed on the SourceForge servers, for example).
We now provide the "-H" flag and the "notify.legacyMail" configuration
key for these cases.

tools/git-notify

@@ -18,6 +18,7 @@
 #   -A        Omit the author name from the mail subject
 #   -C        Show committer in the body if different from the author
 #   -c name   Send CIA notifications under specified project name
+#   -H        The mail(1) utility doesn't accept headers via "-a"
 #   -m addr   Send mail notifications to specified address
 #   -n max    Set max number of individual mails to send
 #   -r name   Set the git repository name
@@ -53,6 +54,9 @@ my $debug = 0;
 
 # configuration parameters
 
+# the $mailer doesn't accept headers via "-a" (can be set with the -H option)
+my $legacy_mail = git_config( "notify.legacymail" );
+
 # omit the author from the mail subject (can be set with the -A option)
 my $omit_author = git_config( "notify.omitauthor" );
 
@@ -104,6 +108,7 @@ sub usage()
     print "   -A        Omit the author name from the mail subject\n";
     print "   -C        Show committer in the body if different from the author\n";
     print "   -c name   Send CIA notifications under specified project name\n";
+    print "   -H        The mail(1) utility doesn't accept headers via `-a'\n";
     print "   -m addr   Send mail notifications to specified address\n";
     print "   -n max    Set max number of individual mails to send\n";
     print "   -r name   Set the git repository name\n";
@@ -291,6 +296,7 @@ sub parse_options()
         elsif ($arg eq '-A') { $omit_author = 1; }
         elsif ($arg eq '-C') { $show_committer = 1; }
         elsif ($arg eq '-c') { $cia_project_name = shift @ARGV; }
+        elsif ($arg eq '-H') { $legacy_mail = 1; }
         elsif ($arg eq '-m') { $commitlist_address = shift @ARGV; }
         elsif ($arg eq '-n') { $max_individual_notices = shift @ARGV; }
         elsif ($arg eq '-r') { $repos_name = shift @ARGV; }
@@ -333,7 +339,13 @@ sub mail_notification($$$@)
         return unless defined $pid;
         if (!$pid)
         {
-            exec $mailer, "-s", $subject, "-a", "Content-Type: $content_type", $name or die "Cannot exec $mailer";
+            my @mailer_options = ( "-s", $subject );
+
+            unless ($legacy_mail)
+            {
+                push @mailer_options, "-a", "Content-Type: $content_type";
+            }
+            exec $mailer, @mailer_options, $name or die "Cannot exec $mailer";
         }
         binmode MAIL, ":utf8";
         print MAIL join("\n", @text), "\n";