Subject: Re: [PATCH v2 1/2] sendemail: teach git-send-email to list aliases

From: Eric Sunshine <[email-masked]>
Date: Tue, 17 Nov 2015 02:20:49 -0500

On Tue, Nov 17, 2015 at 12:10:35AM +0000, Keller, Jacob E wrote:
> On Mon, 2015-11-16 at 18:50 -0500, Eric Sunshine wrote:
> > It should be possible to extract the alias within the shell itself
> > without a separate process. For instance:
> > 
> >     read alias rest
> > 
> > will leave the first token in $alias and the remainder of the line in
> > $rest, and it's all done within the shell process.
> 
> I'll look into this :)

My reason for asking is concern about scripts possibly breaking if
someone comes along and wants to "fix" --dump-aliases to also dump
the alias expansions. One possibility is just to punt today and say
that when that feature is needed in the future, then that someone can
add a --verbose option to complement --dump-aliases which would emit
the alias expansions as well. One nice thing about punting at this
point is that we don't (today) have to define a format for the output
of the expansions. If we did want to think about it, one verbose,
non-ambiguous format would be to show the alias name on a line by
itself, and each expansion value on a line by itself indented by a
tab. For instance:

    managers
        bob
	fred
    devs
        jane
	john

> > Also, shouldn't --list-aliases (or --dump-aliases) be mutually
> > exclusive with many of the other options? New tests would check such
> > exclusivity as well.
> 
> I am at a loss for how to do that correctly in the perl. Help would be
> appreciated here.

Since git-send-email.perl already configures GetOpt::Long with the
'pass_through' option, one possibility would be to invoke
GetOptions() once for --list-aliases (or --dump-aliases), and then
again for the normal options. Doing so may be a bit ugly; on the
other hand, it does indicate pretty clearly that --list-aliases is a
distinct "mode" of operation. On top of your patch, it might look
something like this:

--- 8< ---
diff --git a/git-send-email.perl b/git-send-email.perl
index ee14894..cada5ea 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -296,6 +296,12 @@ $SIG{INT}  = \&signal_handler;
 
 my $help;
 my $rc = GetOptions("h" => \$help,
+		    "list-aliases" => \$list_aliases);
+usage() unless $rc;
+die "--list-aliases incompatible with other options\n"
+	if !$help and $list_aliases and @ARGV;
+
+$rc = GetOptions(
 		    "sender|from=s" => \$sender,
                     "in-reply-to=s" => \$initial_reply_to,
 		    "subject=s" => \$initial_subject,
@@ -349,7 +355,6 @@ my $rc = GetOptions("h" => \$help,
 		    "force" => \$force,
 		    "xmailer!" => \$use_xmailer,
 		    "no-xmailer" => sub {$use_xmailer = 0},
-                    "list-aliases" => \$list_aliases,
 	 );
 
 usage() if $help;
--- 8< ---

Though, it may be overkill for this minor use-case.