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authorIan Jackson <>2016-10-20 15:55:57 +0100
committerIan Jackson <>2016-10-20 16:10:49 +0100
commit50048b4c1c41e1471cdc7054bed02ff30418ea44 (patch)
parenta17cad7ce9f5d5a89c77cd9179d4fb33076e493f (diff)
split brain cache: Add a dummy ref update when necessary
git-update-ref does not make a new reflog entry if the ref is not actually being changed. This can mean that `dgit build' might fail to find a good cache entry, but also fail to generate one that push will accept. In this case, generate a dummy reflog update. We make a spurious child of the $dgitview, as that's straightforward. Giving it the same tree and a parent means that human use of reflog commands will produce empty results rather than lots of confusing output. Signed-off-by: Ian Jackson <>
2 files changed, 20 insertions, 0 deletions
diff --git a/debian/changelog b/debian/changelog
index 99e724d..08b3e32 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -6,6 +6,10 @@ dgit (2.4~) unstable; urgency=low
* split brain cache: Fix a wrong implicit reference to $_.
+ * split brain cache: Make sure to write reflog entries for cache updates
+ even if the eventual tree (and therefore commit) is the same.
+ Otherwise, after updating dgit, the cache might have the right answer
+ but not be refreshed even by a build.
diff --git a/dgit b/dgit
index 9fcd1fc..7ca97c5 100755
--- a/dgit
+++ b/dgit
@@ -3917,6 +3917,22 @@ END
ensuredir ".git/logs/refs/dgit-intern";
my $makelogfh = new IO::File ".git/logs/refs/$splitbraincache", '>>'
or die $!;
+ my $oldcache = git_get_ref "refs/$splitbraincache";
+ if ($oldcache eq $dgitview) {
+ my $tree = cmdoutput qw(git rev-parse), "$dgitview:";
+ # git update-ref doesn't always update, in this case. *sigh*
+ my $dummy = make_commit_text <<END;
+tree $tree
+parent $dgitview
+author Dgit <dgit\> 1000000000 +0000
+committer Dgit <dgit\> 1000000000 +0000
+Dummy commit - do not use
+ runcmd @git, qw(update-ref -m), "dgit $our_version - dummy",
+ "refs/$splitbraincache", $dummy;
+ }
runcmd @git, qw(update-ref -m), $cachekey, "refs/$splitbraincache",