hit - git-style interface for project helper scripts

hit.sh

#!/usr/bin/env bash
set -euo pipefail && cd "$(dirname "${BASH_SOURCE[0]}")/.."

# hit - git-like command dispatcher. Who needs Makefiles?
#
# Create a directory `bin/` at the top level of your project
# directory (the one committed to git). Copy this file into
# that folder, call it `hit` and make it executable.
#
# Type `bin/hit NAME` to run a subcommand called NAME. Subcommands
# delegate to executables named `hit-NAME` in the `bin/` folder.
#
# Type `bin/hit help` to list all available subcommands.
#
# A subcommand NAME is implemented as an executable file called
# `bin/hit-NAME`. Here's on implemented in bash:
#
#    #!/usr/bin/env bash
#    set -euo pipefail && cd "$(dirname "${BASH_SOURCE[0]}")/.."
#    ## $DESCRIPTION: Clear build artifacts
#    rm -rf build
#
# Note that subcommands can be implemented in any language (python, perl, ...)
#
#
# Best used by adding the `bin/` directory to your PATH by
# configuring a per-project-folder PATH in your `.envrc`. See https://direnv.net/
# This allows you to simply type `hit NAME`.
#
# `hit` automatically changes to the project root folder before
# doing anything else so `hit` commands can be run from anywhere
# inside the project hierarcyh.

bin_dir=bin
commands=("$bin_dir/hit-"*)

help() {

    echo 'Syntax: hit <command> [arguments]'
    echo
    echo The following commands are available:
    echo

    for command in "${commands[@]}"; do
        name="$(basename $command | sed 's/hit-//')"
        description=$(perl -ne '/\$DESCRIPTION: (.*)/ && print "$1\n"' < "$command")
        echo -en "    $name"
        seq -f " " -s '' $((15 - ${#name}))
        printf "%s\n" "$description"
    done
    echo
    echo "    help           Show this help"
    echo
}

run() {
    command="${1-}"
    if [[ "$command" == "" || "$command" == "help" || "$command" == "--help" ]]; then
        help
    else
        shift
        fname="$bin_dir/hit-$command"
        if [[ -x "$fname" ]]; then
            "$fname" "$@"
        else
            echo "Command not found: $command"
            echo
            help
            exit 1
        fi
    fi
}

run "$@"