git-svn: factor out _collapse_dotdot function

The SVN API functions will not accept ../foo but their canonicalization
functions will not collapse it.  So we'll have to do it ourselves.

_collapse_dotdot() works better than the existing regex did.

This will be used shortly when canonicalize_path() starts using the
SVN API.

[ew: commit title]

Signed-off-by: Eric Wong <normalperson@yhbt.net>

perl/Git/SVN/Utils.pm

@@ -72,6 +72,18 @@ API as a file path.
 
 =cut
 
+# Turn foo/../bar into bar
+sub _collapse_dotdot {
+	my $path = shift;
+
+	1 while $path =~ s{/[^/]+/+\.\.}{};
+	1 while $path =~ s{[^/]+/+\.\./}{};
+	1 while $path =~ s{[^/]+/+\.\.}{};
+
+	return $path;
+}
+
+
 sub canonicalize_path {
 	my ($path) = @_;
 	my $dot_slash_added = 0;
@@ -83,7 +95,7 @@ sub canonicalize_path {
 	# good reason), so let's do this manually.
 	$path =~ s#/+#/#g;
 	$path =~ s#/\.(?:/|$)#/#g;
-	$path =~ s#/[^/]+/\.\.##g;
+	$path = _collapse_dotdot($path);
 	$path =~ s#/$##g;
 	$path =~ s#^\./## if $dot_slash_added;
 	$path =~ s#^/##;

t/Git-SVN/Utils/collapse_dotdot.t

@@ -0,0 +1,23 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+
+use Test::More 'no_plan';
+
+use Git::SVN::Utils;
+my $collapse_dotdot = \&Git::SVN::Utils::_collapse_dotdot;
+
+my %tests = (
+	"foo/bar/baz"			=> "foo/bar/baz",
+	".."				=> "..",
+	"foo/.."			=> "",
+	"/foo/bar/../../baz"		=> "/baz",
+	"deeply/.././deeply/nested"	=> "./deeply/nested",
+);
+
+for my $arg (keys %tests) {
+	my $want = $tests{$arg};
+
+	is $collapse_dotdot->($arg), $want, "_collapse_dotdot('$arg') => $want";
+}