1 files changed, 20 insertions, 0 deletions
diff --git a/parent-prune-empty-merge b/parent-prune-empty-merge
new file mode 100755
index 0000000..10e9fb8
--- /dev/null
+++ b/parent-prune-empty-merge
@@ -0,0 +1,20 @@
+#!/usr/bin/env ruby
+# Usage: git filter-branch -f --parent-filter ~/git-filters/parent-prune-empty-merge HEAD
+
+# Function to determine if commit 'c' already an ancestor of any of
+# the commits given in 'commits'
+def subsumed_by(c,commits)
+  commits.any? do |c2|
+    c!=c2 && c==`git merge-base #{c} #{c2}`.chomp()
+  end
+end
+
+# Get the current list of parents
+parents = $stdin.read.split.select{|a|a!='-p'}
+
+# Pnly keep parents that are not subsumed by other parents.
+parents = parents.select do |p|
+  not subsumed_by(p,parents)
+end
+
+puts parents.uniq.map{|p|"-p #{p}"}.join(' ')