git-graph.sh

#!/bin/bash

# Given a grep expression, create a graph of occurrences of that expression
# in your code's history.

set -e

expr="$1"

datafile=$(mktemp)
echo 'ago count' > $datafile
for ago in $(seq 90 -1 0); do
    echo -n '.'
    commit=$(git rev-list -1 --until="$ago days ago" origin/trunk)
    count=$(git grep -E "$expr" $commit -- '*.cc' '*.h' '*.m' '*.mm' | wc -l)
    echo "-$ago $count" >> $datafile
done

R CMD BATCH <(cat <<EOF
data = read.delim("$datafile", sep=' ')
png(width=600, height=300)
plot(count ~ ago, type="l", main="$expr", xlab='days ago', data=data)
EOF
) /dev/null

echo done.