git/contrib/stats/git-common-hash

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#!/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;
}
'