From 0329eb76d525c6a7cd8a331697cd1d6b969314ea Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Wed, 1 Feb 2012 18:38:05 +0000
Subject: [PATCH] update: find best merge source

---
 tb-update.pl | 45 ++++++++++++++++++++-------------------------
 1 file changed, 20 insertions(+), 25 deletions(-)

diff --git a/tb-update.pl b/tb-update.pl
index 18acbc5..6005d9e 100755
--- a/tb-update.pl
+++ b/tb-update.pl
@@ -29,13 +29,25 @@ sub merge_base ($$) {
 		});
 }
 
-sub committ_date ($) {
+sub commit_date ($) {
     my ($ref) = @_;
     my $l = run_git_1line(qw(git-log --date=raw -n1 --pretty=format:%cd), $ref);
     $l =~ m/^(\d+)\s/ or die;
     return $l;
 }
 
+sub compare_source_ages ($$) {
+    my ($r,$s) = @_; # refs, returns something like  age($r) cmp age($s)
+    our %memos;
+    return memo(\%memos, "$r $s", sub {
+	my $mb = merge_base($r, $s);
+	return -($mb eq $r) cmp ($mb eq $s)
+	    # if merge base is $a then $a must be before $b
+	    # ie the commit equal to the merge base is earlier
+	    or (commit_date($r) cmp commit_date($s));
+    });
+}
+
 sub update_base ($) {
     my ($patch) = @_;
 
@@ -108,30 +120,13 @@ sub update_base ($) {
 	# ie we are ahead of the source.  Skip those sources.
 	@sources = grep { $source->{MergeBase} ne $source->{Head} } @sources;
 
-	our %cmp_memos;
-	@sources = sort { 
-	    memo(\%cmp_memos, "$a->{Name} $b->{Name}", sub {
-		my $mb = merge_base($a->{Ref}, $b->{Ref});
-		return -($mb eq $a->{Ref}) cmp ($mb eq $b->{Ref})
-		    # if merge base is $a then $a must be before $b
-		    # ie the commit equal to the merge base is earlier
-		    or (committ_date($a->{Ref}) cmp committ_date($b->{Ref}));
-	    })
-	} @sources;
-	fixme we do not need to sort, only find best, and then do again
-
-	# Now we run git-rev-list to walk the graph back to those
-	# sources so we can tell which is the most recent.
-	foreach my $source (@sources) {
-	    
-
-    
-	    $source->{MergeBase} = $mergebase;
-	    
-	    bad_metadata("$patch base topgit $obj") unless $obj eq 'blob';
-	    
-	    # ok
-	} elsif ($obk 
+	my $best = $sources[0];
+	foreach my $source (@sources[1..$#sources]) {
+	    next if compare_source_ages($best->{Ref}, $source->{Ref}) <= 0;
+	    $best = $source;
+		
+	}
+	
 
 
 sub done ($) { 
-- 
2.30.2