ExtUtils-ParseXS: add author/mksnapshot.pl utility

Crude tool to collect before and after snapshots of all .c files created
by xsubpp, in order to see what (if anything) has changed in
functionality while working on ParseXS files.

MANIFEST

@@ -4157,6 +4157,7 @@ dist/ExtUtils-CBuilder/t/01-basic.t					tests for ExtUtils::CBuilder
 dist/ExtUtils-CBuilder/t/02-link.t					tests for ExtUtils::CBuilder
 dist/ExtUtils-CBuilder/t/03-cplusplus.t					tests for ExtUtils::CBuilder
 dist/ExtUtils-CBuilder/t/04-base.t					tests for ExtUtils::CBuilder
+dist/ExtUtils-ParseXS/author/mksnapshot.pl			Utility for detecting before/after changes to xsubpp output
 dist/ExtUtils-ParseXS/Changes					ExtUtils::ParseXS change log
 dist/ExtUtils-ParseXS/lib/ExtUtils/ParseXS.pm			converts Perl XS code into C code
 dist/ExtUtils-ParseXS/lib/ExtUtils/ParseXS.pod			ExtUtils::ParseXS documentation

Porting/exec-bit.txt

@@ -20,6 +20,7 @@ dist/Devel-PPPort/devel/regenerate
 dist/Devel-PPPort/devel/scanprov
 dist/Devel-PPPort/devel/update_release_date.pl
 dist/Devel-PPPort/soak
+dist/ExtUtils-ParseXS/author/mksnapshot.pl
 dist/Thread-Queue/examples/callback.pl
 dist/Thread-Queue/examples/queue.pl
 installperl

dist/ExtUtils-ParseXS/author/mksnapshot.pl

@@ -0,0 +1,69 @@
+#!/usr/bin/perl
+#
+# mksnapshot.pl
+#
+# This is a very crude script to help check whether and/or what has
+# changed in generated .c files as a result of changes to xsubpp and its
+# modules.
+#
+# It finds all .xs files under the current directory, then copies to
+# another directory, each associated .c file if it exists.
+#
+# The idea is that, while cd'ed to the base of the perl distribution, you
+# run this script, which will copy all the generated .c files to one
+# directory. You then rebuild perl with the newly modified xsubpp, and
+# create a second snapshot to another directory, then compare the results.
+#
+# For example,
+#
+#    ... build perl...
+#
+#    $ mkdir /tmp/snap1 /tmp/snap2
+#    $ dist/ExtUtils-ParseXS/author/mksnapshot.pl /tmp/snap1
+#    $ git clean -xdf
+#
+#    ... modify xsubpp ...
+#    ... build perl...
+#
+#    $ dist/ExtUtils-ParseXS/author/mksnapshot.pl /tmp/snap2
+#    $ diff -ru /tmp/snap[12]
+#
+# Each snapped .c file is saved with each '/' component of its pathname
+# changed to a '='. So ext/POSIX/POSIX.c would be copied to
+#    /tmp/snap1/ext=POSIX=POSIX.c
+
+use warnings;
+use strict;
+
+use File::Find;
+use File::Copy;
+
+die "usage: $0 snapdirectory\n" unless @ARGV == 1;
+my $snapdir = shift @ARGV;
+
+die "No such directory: $snapdir\n" unless -d $snapdir;
+
+find(
+    {
+        wanted   => \&wanted,
+        no_chdir => 1,
+    },
+
+    '.'
+);
+
+
+
+sub wanted {
+    return unless /\.xs$/;
+    my $f = $_;
+    $f =~ s/\.xs$/.c/ or die;
+    return unless -f $f;
+    my $df = $f;
+    $df =~ s{^/}{};
+    $df =~ s{^\./}{};
+    $df =~ s{/}{=}g;
+    $df = "$snapdir/$df";
+    print "snapping $f\n";
+    copy($f, $df) or die "Can't copy $f to $df: $!\n";
+}