git-svn: reduce check_cherry_pick cache overhead

We do not need to store entire lists of commits, only the
number of incomplete and the first commit for reference.
This reduces the amount of data we need to store in memory
and on disk stores.

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

perl/Git/SVN.pm

@@ -1537,7 +1537,7 @@ sub _rev_list {
 	@rv;
 }
 
-sub check_cherry_pick {
+sub check_cherry_pick2 {
 	my $base = shift;
 	my $tip = shift;
 	my $parents = shift;
@@ -1552,7 +1552,8 @@ sub check_cherry_pick {
 			delete $commits{$commit};
 		}
 	}
-	return (keys %commits);
+	my @k = (keys %commits);
+	return (scalar @k, $k[0]);
 }
 
 sub has_no_changes {
@@ -1597,7 +1598,7 @@ sub tie_for_persistent_memoization {
 		mkpath([$cache_path]) unless -d $cache_path;
 
 		my %lookup_svn_merge_cache;
-		my %check_cherry_pick_cache;
+		my %check_cherry_pick2_cache;
 		my %has_no_changes_cache;
 		my %_rev_list_cache;
 
@@ -1608,11 +1609,11 @@ sub tie_for_persistent_memoization {
 			LIST_CACHE => ['HASH' => \%lookup_svn_merge_cache],
 		;
 
-		tie_for_persistent_memoization(\%check_cherry_pick_cache,
-		    "$cache_path/check_cherry_pick");
-		memoize 'check_cherry_pick',
+		tie_for_persistent_memoization(\%check_cherry_pick2_cache,
+		    "$cache_path/check_cherry_pick2");
+		memoize 'check_cherry_pick2',
 			SCALAR_CACHE => 'FAULT',
-			LIST_CACHE => ['HASH' => \%check_cherry_pick_cache],
+			LIST_CACHE => ['HASH' => \%check_cherry_pick2_cache],
 		;
 
 		tie_for_persistent_memoization(\%has_no_changes_cache,
@@ -1636,7 +1637,7 @@ sub tie_for_persistent_memoization {
 		$memoized = 0;
 
 		Memoize::unmemoize 'lookup_svn_merge';
-		Memoize::unmemoize 'check_cherry_pick';
+		Memoize::unmemoize 'check_cherry_pick2';
 		Memoize::unmemoize 'has_no_changes';
 		Memoize::unmemoize '_rev_list';
 	}
@@ -1648,7 +1649,8 @@ sub tie_for_persistent_memoization {
 		return unless -d $cache_path;
 
 		for my $cache_file (("$cache_path/lookup_svn_merge",
-				     "$cache_path/check_cherry_pick",
+				     "$cache_path/check_cherry_pick", # old
+				     "$cache_path/check_cherry_pick2",
 				     "$cache_path/has_no_changes")) {
 			for my $suffix (qw(yaml db)) {
 				my $file = "$cache_file.$suffix";
@@ -1817,15 +1819,15 @@ sub find_extra_svn_parents {
 		}
 
 		# double check that there are no missing non-merge commits
-		my (@incomplete) = check_cherry_pick(
+		my ($ninc, $ifirst) = check_cherry_pick2(
 			$merge_base, $merge_tip,
 			$parents,
 			@all_ranges,
 		       );
 
-		if ( @incomplete ) {
-			warn "W:svn cherry-pick ignored ($spec) - missing "
-				.@incomplete." commit(s) (eg $incomplete[0])\n";
+		if ($ninc) {
+			warn "W:svn cherry-pick ignored ($spec) - missing " .
+				"$ninc commit(s) (eg $ifirst)\n";
 		} else {
 			warn
 				"Found merge parent ($spec): ",