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>

perl/Git/SVN/Utils.pm

@@ -0,0 +1,59 @@
+package Git::SVN::Utils;
+
+use strict;
+use warnings;
+
+use base qw(Exporter);
+
+our @EXPORT_OK = qw(fatal can_compress);
+
+
+=head1 NAME
+
+Git::SVN::Utils - utility functions used across Git::SVN
+
+=head1 SYNOPSIS
+
+    use Git::SVN::Utils qw(functions to import);
+
+=head1 DESCRIPTION
+
+This module contains functions which are useful across many different
+parts of Git::SVN.  Mostly it's a place to put utility functions
+rather than duplicate the code or have classes grabbing at other
+classes.
+
+=head1 FUNCTIONS
+
+All functions can be imported only on request.
+
+=head3 fatal
+
+    fatal(@message);
+
+Display a message and exit with a fatal error code.
+
+=cut
+
+# Note: not certain why this is in use instead of die.  Probably because
+# the exit code of die is 255?  Doesn't appear to be used consistently.
+sub fatal (@) { print STDERR "@_\n"; exit 1 }
+
+
+=head3 can_compress
+
+    my $can_compress = can_compress;
+
+Returns true if Compress::Zlib is available, false otherwise.
+
+=cut
+
+my $can_compress;
+sub can_compress {
+	return $can_compress if defined $can_compress;
+
+	return $can_compress = eval { require Compress::Zlib; };
+}
+
+
+1;