--- /dev/null
+#!/bin/sh
+
+# This script displays the distribution of longest common hash prefixes.
+# This can be used to determine the minimum prefix length to use
+# for object names to be unique.
+
+git rev-list --objects --all | sort | perl -lne '
+ substr($_, 40) = "";
+ # uncomment next line for a distribution of bits instead of hex chars
+ # $_ = unpack("B*",pack("H*",$_));
+ if (defined $p) {
+ ($p ^ $_) =~ /^(\0*)/;
+ $common = length $1;
+ if (defined $pcommon) {
+ $count[$pcommon > $common ? $pcommon : $common]++;
+ } else {
+ $count[$common]++; # first item
+ }
+ }
+ $p = $_;
+ $pcommon = $common;
+ END {
+ $count[$common]++; # last item
+ print "$_: $count[$_]" for 0..$#count;
+ }
+'