git-purge

#!/bin/bash
shopt -s extglob;

# If user requested help, print it.
_chkHelp() {
    case "${1}" in        
        +(-)[hH]*([eE][lL][pP]) )
            _help 0;
            ;;
        * )
            return
            ;;
    esac;
}

# Print help and exit.
_help() {
    local path="$0";
    local script=${path##*/};
    cat << EOH >&2
Usage:
  ${script} <file>
Decription:
  Purge a file from the entire history of a git repo.
EOH

    if [ "${1}" ]; then
        exit "${1}";
    fi;
    exit 1;
}

# Set console color.
# Optionally, run a command afterwards, and once the command returns,
#   reset the console color to normal.
_c() {
    local -A Codes=( 
        ["black"]="0" 
        ["red"]="1" 
        ["green"]="2" 
        ["yellow"]="3" 
        ["blue"]="4" 
        ["magenta"]="5" 
        ["cyan"]="6" 
        ["white"]="7" 
    );

    local k c;
    for k in "${!Codes[@]}"; do
        [ "${k}" = "${1}" ] &&
            c="${Codes[$k]}";
    done;

    [ -n "${c}" ] &&
        tput setaf "${c}";
    
    [ -z "${*:2}" ] &&
        return;

    eval "${@:2}";
    tput sgr0;
}

# Set the console color to bold.
# Optionally, pass any arguments to function '_c'.
_C() {
    tput bold;
    [ -n "$*" ] &&
        _c "$@";
}

# Reset console color to normal.
_u() {
    tput sgr0;
}

# Ask user to answer a "yes or no" question.
# Analyse the user's answer, with NO as the default.
_yN() {
    local -i t="${1}";

    local ans;
    [ "${t}" != 0 ] &&
        read -t "${t}" -p "${*:2}" ans ||
        read -p "$*" ans;

    case "${ans}" in [yY] | [yY][eE][sS])
        return 0;
    esac;
    return 1;
}

# Purge a file from the entire history of a git repo.
_purge() {
    local file="${1}";

    _c green echo "${file}";


    echo "  git filter-branch --force --index-filter \\";
    echo "  'git rm --cached --ignore-unmatch ${file}' \\";
    echo "  --prune-empty --tag-name-filter cat -- --all";

    local purgeCmd=(
        git filter-branch --force --index-filter
        \'git rm --cached --ignore-unmatch ${file}\'
        --prune-empty --tag-name-filter cat -- --all
    );
    eval ${purgeCmd[@]};
}

# Force-push the changes to the git repo.
_pushForce() {
    _C green;
    printf "==>";
    _C white;
    printf " Push changes to git repo? [y/N]: ";
    _u;
    if ! _yN; then
        return;
    fi;

    echo "  git push origin --force --all";
    git push origin --force --all;
    echo "  git push origin --force --tags";
    git push origin --force --tags;
}

_chkHelp "${1}";

declare FILE;
for FILE; do
    _purge "${FILE}";
    [ $? != 0 ] &&
        continue;
    _pushForce;
done;