sendemail: teach git-send-email to dump alias names

Add an option "--dump-aliases" which changes the default behavior of
git-send-email. This mode will simply read the alias files configured by
sendemail.aliasesfile and sendemail.aliasfiletype and dump a list of all
configured aliases, one per line. The intended use case for this option
is the bash-completion script which will use it to autocomplete aliases
on the options which take addresses.

Add some tests for the new option using various alias file formats.

A possible future extension to the alias dump format could be done by
extending the --dump-aliases to take an optional argument defining the
format to display. This has not been done in this patch as no user of
this information has been identified.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>

Documentation/git-send-email.txt

@@ -10,6 +10,7 @@ SYNOPSIS
 --------
 [verse]
 'git send-email' [options] <file|directory|rev-list options>...
+'git send-email' --dump-aliases
 
 
 DESCRIPTION
@@ -387,6 +388,16 @@ default to '--validate'.
 	Send emails even if safety checks would prevent it.
 
 
+Information
+~~~~~~~~~~~
+
+--dump-aliases::
+	Instead of the normal operation, dump the shorthand alias names from
+	the configured alias file(s), one per line in alphabetical order. Note,
+	this only includes the alias name and not its expanded email addresses.
+	See 'sendemail.aliasesfile' for more information about aliases.
+
+
 CONFIGURATION
 -------------
 

git-send-email.perl

@@ -46,6 +46,7 @@ package main;
 sub usage {
 	print <<EOT;
 git send-email [options] <file | directory | rev-list options >
+git send-email --dump-aliases
 
   Composing:
     --from                  <str>  * Email From:
@@ -101,6 +102,9 @@ sub usage {
                                      `git format-patch` ones.
     --force                        * Send even if safety checks would prevent it.
 
+  Information:
+    --dump-aliases                 * Dump configured aliases and exit.
+
 EOT
 	exit(1);
 }
@@ -180,6 +184,7 @@ sub format_2822_time {
 my $format_patch;
 my $compose_filename;
 my $force = 0;
+my $dump_aliases = 0;
 
 # Handle interactive edition of files.
 my $multiedit;
@@ -291,6 +296,11 @@ sub signal_handler {
 
 my $help;
 my $rc = GetOptions("h" => \$help,
+                    "dump-aliases" => \$dump_aliases);
+usage() unless $rc;
+die "--dump-aliases incompatible with other options\n"
+    if !$help and $dump_aliases and @ARGV;
+$rc = GetOptions(
 		    "sender|from=s" => \$sender,
                     "in-reply-to=s" => \$initial_reply_to,
 		    "subject=s" => \$initial_subject,
@@ -551,6 +561,11 @@ sub parse_sendmail_aliases {
 	}
 }
 
+if ($dump_aliases) {
+    print "$_\n" for (sort keys %aliases);
+    exit(0);
+}
+
 # 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 {

t/t9001-send-email.sh

@@ -1555,6 +1555,88 @@ test_expect_success $PREREQ 'sendemail.aliasfile=~/.mailrc' '
 	grep "^!someone@example\.org!$" commandline1
 '
 
+test_dump_aliases () {
+	msg="$1" && shift &&
+	filetype="$1" && shift &&
+	printf '%s\n' "$@" >expect &&
+	cat >.tmp-email-aliases &&
+
+	test_expect_success $PREREQ "$msg" '
+		clean_fake_sendmail && rm -fr outdir &&
+		git config --replace-all sendemail.aliasesfile \
+			"$(pwd)/.tmp-email-aliases" &&
+		git config sendemail.aliasfiletype "$filetype" &&
+		git send-email --dump-aliases 2>errors >actual &&
+		test_cmp expect actual
+	'
+}
+
+test_dump_aliases '--dump-aliases sendmail format' \
+	'sendmail' \
+	'abgroup' \
+	'alice' \
+	'bcgrp' \
+	'bob' \
+	'chloe' <<-\EOF
+	alice: Alice W Land <awol@example.com>
+	bob: Robert Bobbyton <bob@example.com>
+	chloe: chloe@example.com
+	abgroup: alice, bob
+	bcgrp: bob, chloe, Other <o@example.com>
+	EOF
+
+test_dump_aliases '--dump-aliases mutt format' \
+	'mutt' \
+	'alice' \
+	'bob' \
+	'chloe' \
+	'donald' <<-\EOF
+	alias alice Alice W Land <awol@example.com>
+	alias donald Donald C Carlton <donc@example.com>
+	alias bob Robert Bobbyton <bob@example.com>
+	alias chloe chloe@example.com
+	EOF
+
+test_dump_aliases '--dump-aliases mailrc format' \
+	'mailrc' \
+	'alice' \
+	'bob' \
+	'chloe' \
+	'eve' <<-\EOF
+	alias alice   Alice W Land <awol@example.com>
+	alias eve     Eve <eve@example.com>
+	alias bob     Robert Bobbyton <bob@example.com>
+	alias chloe   chloe@example.com
+	EOF
+
+test_dump_aliases '--dump-aliases pine format' \
+	'pine' \
+	'alice' \
+	'bob' \
+	'chloe' \
+	'eve' <<-\EOF
+	alice	Alice W Land	<awol@example.com>
+	eve	Eve	<eve@example.com>
+	bob	Robert	Bobbyton <bob@example.com>
+	chloe		chloe@example.com
+	EOF
+
+test_dump_aliases '--dump-aliases gnus format' \
+	'gnus' \
+	'alice' \
+	'bob' \
+	'chloe' \
+	'eve' <<-\EOF
+	(define-mail-alias "alice" "awol@example.com")
+	(define-mail-alias "eve" "eve@example.com")
+	(define-mail-alias "bob" "bob@example.com")
+	(define-mail-alias "chloe" "chloe@example.com")
+	EOF
+
+test_expect_success '--dump-aliases must be used alone' '
+	test_must_fail git send-email --dump-aliases --to=janice@example.com -1 refs/heads/accounting
+'
+
 test_sendmail_aliases () {
 	msg="$1" && shift &&
 	expect="$@" &&