A bash script that generates a report about contributions to a Git repository.

git-contributions.bash

#!/bin/bash

# ====================================================================================================
# The script below allows to have a quick overview of contributions on a Git repository. Bash 4+ is required.
# Especially useful when we do not have access to graphs like those that we can find on Github.
#
# This script handles three non-mandatory parameters:
#  - START is used to keep commits only since the given date (default = 01 Jan 2000).
#  - END is used to keep commits only until the given date (default = 01 Jan 2050).
#  - MINIMUM is used to define the minimum number of commits in order to appear in the report (default = 10).
# ====================================================================================================

START="${1}" ; END="${2}" ; MINIMUM="${3}"

function define_criteria()
{
    if [[ ! -z "${START}" ]]; then
        SINCE="--since=\"${START}\""
    else
        SINCE="--since=\"01 Jan 2000\""
    fi

    if [[ ! -z "${END}" ]]; then
        UNTIL="--until=\"${END}\""
    else
        UNTIL="--until=\"01 Jan 2050\""
    fi

    if [[ -z "${MINIMUM}" ]]; then
        MINIMUM=10
    fi
}

function extract_stats()
{
    declare -A AUTHORS_IDENTITY
    declare -A RAW_STATS

    while read -r LINE; do
        if [[ "${LINE}" =~ ^([[:digit:]]+)[[:space:]](.+)[[:space:]]\<(.+)\>$ ]]; then
            AUTHOR_COMMITS="${BASH_REMATCH[1]}"
            AUTHOR_NAME="${BASH_REMATCH[2]}"
            AUTHOR_EMAIL="${BASH_REMATCH[3]}"

            if [[ "${RAW_STATS[${AUTHOR_EMAIL}]+isset}" ]]; then
                RAW_STATS["${AUTHOR_EMAIL}"]="$(( ${RAW_STATS["${AUTHOR_EMAIL}"]} + ${AUTHOR_COMMITS} ))"
            else
                AUTHORS_IDENTITY["${AUTHOR_EMAIL}"]="${AUTHOR_NAME}"
                RAW_STATS["${AUTHOR_EMAIL}"]="${AUTHOR_COMMITS}"
            fi
        fi
    done <<< "${AUTHORS}"

    for AUTHOR_EMAIL in "${!RAW_STATS[@]}"
    do
        if (( "${RAW_STATS[${AUTHOR_EMAIL}]}" >= "${MINIMUM}" )); then
            echo "${RAW_STATS[${AUTHOR_EMAIL}]} ${AUTHORS_IDENTITY[${AUTHOR_EMAIL}]} <${AUTHOR_EMAIL}>"
        fi
    done | sort -rn
}

function format_report()
{
    OUTPUT="\nRank\tName\tEmail\tCommits\tFiles Changed\tInsertions (+)\tDeletions (-)"
    OUTPUT+="\tDiff/Commits (~)\tFirst Commit\tLast Commit"

    RANK=0
    while read -r LINE; do
        if [[ "${LINE}" =~ ^([[:digit:]]+)[[:space:]](.+)[[:space:]]\<(.+)\>$ ]]; then
            (( RANK+=1 ))

            AUTHOR_COMMITS="${BASH_REMATCH[1]}"
            AUTHOR_NAME="${BASH_REMATCH[2]}"
            AUTHOR_EMAIL="${BASH_REMATCH[3]}"
            FILES=0 ; INSERTIONS=0 ; DELETIONS=0

            eval $(git log --shortstat --author="${AUTHOR_EMAIL}" "${SINCE}" "${UNTIL}" --no-merges | grep -E "fil(e|es) changed" \
                | awk '{ files+=$1; inserted+=$4; deleted+=$6 } END { print "FILES="files, "INSERTIONS="inserted, "DELETIONS="deleted }')

            FIRST_COMMIT="`git log --author="${AUTHOR_EMAIL}" "${SINCE}" "${UNTIL}" --no-merges --reverse --pretty=format:%H | head -1`"
            FIRST_COMMIT_DATE="`git show -s --format=%ar "${FIRST_COMMIT}"`"

            LAST_COMMIT="`git log --author="${AUTHOR_EMAIL}" "${SINCE}" "${UNTIL}" --no-merges --pretty=format:%H | head -1`"
            LAST_COMMIT_DATE="`git show -s --format=%ar "${LAST_COMMIT}"`"

            OUTPUT+="\n${RANK}\t${AUTHOR_NAME}\t${AUTHOR_EMAIL}\t${AUTHOR_COMMITS}\t${FILES}\t${INSERTIONS}\t${DELETIONS}"
            OUTPUT+="\t"$(( (INSERTIONS+DELETIONS) / AUTHOR_COMMITS ))"\t${FIRST_COMMIT_DATE}\t${LAST_COMMIT_DATE}"
        fi
    done <<< "${REFINED_STATS}"
}

function format_footer()
{
    FOOTER="\nThis report has been generated using the "$(tput bold)$(git rev-parse --abbrev-ref HEAD)$(tput sgr0)" branch"

    if [[ ! -z "${START}" && ! -z "${END}" ]]; then
        FOOTER+=" (commits between ${START} and ${END})"
    elif [[ ! -z "${START}" && -z "${END}" ]]; then
        FOOTER+=" (commits since ${START})"
    elif [[ -z "${START}" && ! -z "${END}" ]]; then
        FOOTER+=" (commits until ${END})"
    fi

    FOOTER+="."
}

define_criteria
AUTHORS="`git shortlog -sne "${SINCE}" "${UNTIL}" --no-merges`"
if [[ ! -z "${AUTHORS}" ]]; then
    REFINED_STATS="$(extract_stats)"
    if [[ ! -z "${REFINED_STATS}" ]]; then
        format_report
        echo -e "${OUTPUT}" | column -ts $'\t'

        format_footer
        echo -e "${FOOTER}"
    fi
fi

I have adapted it in Python, you can see it here: https://gist.github.com/akiavara/51d0d9d302013521bb10