[PATCH] git-svn: Destroy the cache when we fail to read it

[Jason Gross <jgross@MIT.EDU>]

Previously, we would fail fatally when trying to fetch changes with
mergeinfo on a 32 bit machine, when the repository previously had
fetched changes with mergeinfo on a 64 bit machine.

This fixes bug 618875 (which is also 587650, 635097).  Much of the code
was written by Jonathan Nieder <jrnieder@gmail.com> with suggestions
from Steffen Mueller <smueller@cpan.org> (see
http://lists.debian.org/debian-perl/2011/05/msg00023.html and
http://lists.debian.org/debian-perl/2011/05/msg00026.html).

Signed-off-by: Jason Gross <jgross@mit.edu>
Cc: Jonathan Nieder <jrnieder@gmail.com>
---
 git-svn.perl |   59 +++++++++++++++++++++++++++++++++++----------------------
 1 files changed, 36 insertions(+), 23 deletions(-)

diff --git a/git-svn.perl b/git-svn.perl
index 89f83fd..78ccdc8 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -1680,7 +1680,7 @@ use vars qw/$default_repo_id $default_ref_id $_no_metadata $_follow_parent
             $_use_svnsync_props $no_reuse_existing $_minimize_url
 	    $_use_log_author $_add_author_from $_localtime/;
 use Carp qw/croak/;
-use File::Path qw/mkpath/;
+use File::Path qw/mkpath rmtree/;
 use File::Copy qw/copy/;
 use IPC::Open3;
 use Memoize;  # core since 5.8.0, Jul 2002
@@ -3198,28 +3198,41 @@ sub has_no_changes {
 		$memoized = 1;
 
 		my $cache_path = "$ENV{GIT_DIR}/svn/.caches/";
-		mkpath([$cache_path]) unless -d $cache_path;
-
-		tie my %lookup_svn_merge_cache => 'Memoize::Storable',
-		    "$cache_path/lookup_svn_merge.db", 'nstore';
-		memoize 'lookup_svn_merge',
-			SCALAR_CACHE => 'FAULT',
-			LIST_CACHE => ['HASH' => \%lookup_svn_merge_cache],
-		;
-
-		tie my %check_cherry_pick_cache => 'Memoize::Storable',
-		    "$cache_path/check_cherry_pick.db", 'nstore';
-		memoize 'check_cherry_pick',
-			SCALAR_CACHE => 'FAULT',
-			LIST_CACHE => ['HASH' => \%check_cherry_pick_cache],
-		;
-
-		tie my %has_no_changes_cache => 'Memoize::Storable',
-		    "$cache_path/has_no_changes.db", 'nstore';
-		memoize 'has_no_changes',
-			SCALAR_CACHE => ['HASH' => \%has_no_changes_cache],
-			LIST_CACHE => 'FAULT',
-		;
+		my $do_memoization = sub {
+			mkpath([$cache_path]) unless -d $cache_path;
+
+			tie my %lookup_svn_merge_cache => 'Memoize::Storable',
+			    "$cache_path/lookup_svn_merge.db", 'nstore';
+			memoize 'lookup_svn_merge',
+				SCALAR_CACHE => 'FAULT',
+				LIST_CACHE => ['HASH' => \%lookup_svn_merge_cache],
+			;
+
+			tie my %check_cherry_pick_cache => 'Memoize::Storable',
+			    "$cache_path/check_cherry_pick.db", 'nstore';
+			memoize 'check_cherry_pick',
+				SCALAR_CACHE => 'FAULT',
+				LIST_CACHE => ['HASH' => \%check_cherry_pick_cache],
+			;
+
+			tie my %has_no_changes_cache => 'Memoize::Storable',
+			    "$cache_path/has_no_changes.db", 'nstore';
+			memoize 'has_no_changes',
+				SCALAR_CACHE => ['HASH' => \%has_no_changes_cache],
+				LIST_CACHE => 'FAULT',
+			;
+		};
+
+		if (not eval {
+			$do_memoization->();
+			1;
+		}) {
+			my $err = $@ || "Zombie error"; # "Zombie error" to catch clobbered $@ in buggy destructors
+			die $err unless -d $cache_path;
+			print STDERR "Discarding cache and trying again ($@)\n";
+			rmtree([$cache_path]);
+			$do_memoization->();
+		}
 	}
 
 	sub unmemoize_svn_mergeinfo_functions {
-- 
1.7.2.3