Split brain: Memoise (cache) split brain dgit-view in a reflog

[dgit.git] / dgit

diff --git a/dgit b/dgit
index 0812f32ae2e48338a2686ffae70bfcb5050bc580..b22d6ab3f25a386194d08d4449de504dd53d6fe5 100755 (executable)
--- a/dgit
+++ b/dgit
@@ -71,6 +71,7 @@ our $suite_re = '[-+.0-9a-z]+';
 our $cleanmode_re = 'dpkg-source(?:-d)?|git|git-ff|check|none';
 
 our $git_authline_re = '^([^<>]+) \<(\S+)\> (\d+ [-+]\d+)$';
+our $splitbraincache = 'dgit-intern/quilt-cache';
 
 our (@git) = qw(git);
 our (@dget) = qw(dget);
@@ -2556,8 +2557,9 @@ sub quiltify_splitbrain_needed () {
     }
 }
 
-sub quiltify_splitbrain ($$$$$) {
-    my ($clogp, $unapplied, $headref, $diffbits, $editedignores) = @_;
+sub quiltify_splitbrain ($$$$$$) {
+    my ($clogp, $unapplied, $headref, $diffbits,
+       $editedignores, $cachekey) = @_;
     if ($quilt_mode !~ m/gbp|dpm/) {
        # treat .gitignore just like any other upstream file
        $diffbits = { %$diffbits };
@@ -2613,8 +2615,17 @@ END
         commit_admin "Commit patch to update .gitignore";
     }
 
-    die 'xxx memoisation via git-reflog';
+    my $dgitview = git_rev_parse 'refs/heads/dgit-view';
+
+    changedir '../../../..';
+    ensuredir ".git/logs/refs/dgit-intern";
+    my $makelogfh = new IO::File ".git/logs/refs/$splitbraincache", '>>'
+      or die $!;
+    runcmd @git, qw(update-ref -m), $cachekey, "refs/$splitbraincache",
+       $dgitview;
+
     die 'xxx fast forward (should not depend on quilt mode, but will always be needed if we did $split_brain)';
+    changedir '.git/dgit/unpack/work';
 }
 
 sub quiltify ($$$$) {
@@ -3026,6 +3037,63 @@ END
     $dscaddfile->($debtar);
     close $fakedsc or die $!;
 
+    my $splitbrain_cachekey;
+    if ($quilt_mode =~ m/gbp|dpm|unapplied/) {
+       # we look in the reflog of dgit-intern/quilt-cache
+       # we look for an entry whose message is the key for the cache lookup
+       my @cachekey = (qw(dgit), $our_version);
+       push @cachekey, $upstreamversion;
+       push @cachekey, $headref;
+
+       push @cachekey, hashfile('fake.dsc');
+
+       my $srcshash = Digest::SHA->new(256);
+       my %sfs = ( %INC, '$0(dgit)' => $0 );
+       foreach my $sfk (sort keys %sfs) {
+           $srcshash->add($sfk,"  ");
+           $srcshash->add(hashfile($sfs{$sfk}));
+           $srcshash->add("\n");
+       }
+       push @cachekey, $srcshash->hexdigest();
+       $splitbrain_cachekey = "@cachekey";
+
+       my @cmd = (@git, qw(reflog), '--pretty=format:%H %gs',
+                  $splitbraincache);
+       printdebug "splitbrain cachekey $splitbrain_cachekey\n";
+       debugcmd "|(probably)",@cmd;
+       my $child = open GC, "-|";  defined $child or die $!;
+       if (!$child) {
+           chdir '../../..' or die $!;
+           if (!stat ".git/logs/refs/$splitbraincache") {
+               $! == ENOENT or die $!;
+               printdebug ">(no reflog)\n";
+               exit 0;
+           }
+           exec @cmd; die $!;
+       }
+       while (<GC>) {
+           chomp;
+           printdebug ">| ", $_, "\n" if $debuglevel > 1;
+           next unless m/^(\w+) (\S.*\S)$/ && $2 eq $splitbrain_cachekey;
+           
+           my $cachehit = $1;
+           quilt_fixup_mkwork($headref);
+           if ($cachehit ne $headref) {
+               progress "quilt fixup ($quilt_mode mode) found cached tree";
+               runcmd @git, qw(checkout -q -b dgit-view), $cachehit;
+               $split_brain = 1;
+               return;
+           }
+           progress "quilt fixup ($quilt_mode mode)".
+             " found cached indication that no changes needed";
+           return;
+       }
+       die $! if GC->error;
+       failedcmd unless close GC;
+
+       printdebug "splitbrain cache miss\n";
+    }
+
     runcmd qw(sh -ec),
         'exec dpkg-source --no-check --skip-patches -x fake.dsc >/dev/null';
 
@@ -3105,9 +3173,10 @@ END
     push @failsuggestion, "Maybe you need to specify one of".
         " --quilt=gbp --quilt=dpm --quilt=unapplied ?";
 
-    if ($quilt_mode =~ m/gbp|dpm|unapplied/) {
+    if ($splitbrain_cachekey) {
        quiltify_splitbrain($clogp, $unapplied, $headref,
-                            $diffbits, \%editedignores);
+                            $diffbits, \%editedignores,
+                           $splitbrain_cachekey);
        return;
     }