Extract some utilities from git-svn to allow extracting Git::SVN.

Put them in a new module called Git::SVN::Utils.  Yeah, not terribly
original and it will be a dumping ground.  But its better than having
them in the main git-svn program.  At least they can be documented
and tested.

* fatal() is used by many classes.
* Change the $can_compress lexical into a function.

This should be enough to extract Git::SVN.

Signed-off-by: Michael G. Schwern <schwern@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Eric Wong <normalperson@yhbt.net>

t/Git-SVN/00compile.t

@@ -0,0 +1,8 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+
+use Test::More tests => 1;
+
+require_ok 'Git::SVN::Utils';

t/Git-SVN/Utils/can_compress.t

@@ -0,0 +1,11 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+use Test::More 'no_plan';
+
+use Git::SVN::Utils qw(can_compress);
+
+# !! is the "convert this to boolean" operator.
+is !!can_compress(), !!eval { require Compress::Zlib };

t/Git-SVN/Utils/fatal.t

@@ -0,0 +1,34 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+use Test::More 'no_plan';
+
+BEGIN {
+	# Override exit at BEGIN time before Git::SVN::Utils is loaded
+	# so it will see our local exit later.
+	*CORE::GLOBAL::exit = sub(;$) {
+	return @_ ? CORE::exit($_[0]) : CORE::exit();
+	};
+}
+
+use Git::SVN::Utils qw(fatal);
+
+# fatal()
+{
+	# Capture the exit code and prevent exit.
+	my $exit_status;
+	no warnings 'redefine';
+	local *CORE::GLOBAL::exit = sub { $exit_status = $_[0] || 0 };
+
+	# Trap fatal's message to STDERR
+	my $stderr;
+	close STDERR;
+	ok open STDERR, ">", \$stderr;
+
+	fatal "Some", "Stuff", "Happened";
+
+	is $stderr, "Some Stuff Happened\n";
+	is $exit_status, 1;
+}