Run only one subtest with Test::More

Apply this patch to Test/More.pm, version 1.302075:

807d806
<     return if exists $ENV{SUBTEST} && $ENV{SUBTEST} ne $_[0];

Here's that patch again, in unified format:

$ diff -u Test/More.pm{,.orig}

--- Test/More.pm      2017-07-27 13:23:56.000000000 +0100

+++ Test/More.pm.orig 2017-07-27 13:19:00.000000000 +0100

@@ -804,7 +804,6 @@

 sub subtest {

     my $tb = Test::More->builder;

+    return if exists $ENV{SUBTEST} && $ENV{SUBTEST} ne $_[0];

     return $tb->subtest(@_);

 }

Run the test like this:

SUBTEST="put name of subtest here" /usr/bin/prove -v test_file.t