Copy a minecraft directory with some symlinks

duplicate-minecraft-dir.sh

#!/bin/bash
# duplicate-minecraft-dir: copies a minecraft directory with some symlinks.
# Requires uname and GNU coreutils.
# Requires admin priv under Windows.
# Dedicated to the public domain under Creative Commons Zero. Do what the heck you wanna do with it.
SELF=$0
die(){ printf '%s: %s\n' "$SELF" "$1">&2; exit "${2-2}"; }
log() { local level=$1; if ((VERBOSE >= level)); then printf '%s: %s\n' "$SELF" "$2">&2; fi; }
nolink=(config options\*.txt launcher_profiles.json servers.dat config baritone Impact mods)

is_windows_admin() { id -G | grep -qE '\<(114|544)\>'; }
case $(uname -o) in
    Cygwin)
        is_windows_admin || die "Gonna need admin privs. Run cygwin as admin!"
        export CYGWIN+=' winsymlinks:nativestrict';;
    Msys)
        is_windows_admin || die "Gonna need admin privs. Run msys as admin!"
        export MSYS+=' winsymlinks:nativestrict';;
esac

usage="Usage: $0 [options] [--] SOURCE TARGET
Copy the minecraft profile in SOURCE to TARGET, allowing for sharing jars and assets by symlinking"
help="Options:
-h      Displays this help.
-a FILE Remove exclusion (a glob).
-e FILE Add exclusion (a glob).
-v      Be verbose.

Default exclusions: ${nolink[*]}."

VERBOSE=0
while getopts ':haev' opt; do
    case $opt in
      (v)   ((VERBOSE++));;
      (a)   for i in "${!nolink[@]}"; do
                if [[ ${nolink[i]} = "$OPTARG" ]]; then
                    unset 'nolink[i]'
                fi
            done;;
      (e)   nolink+=("$OPTARG");;
      (h)   printf '%s\n\n%s\n' "$usage" "$help"
            exit 0;;
      (*)   printf '%s: Invalid option -%s\n%s\n' "$0" "$OPTARG" "$usage">&2
            exit 2;;
    esac
done

shift "$((OPTIND - 1))"
SOURCE=$1
TARGET=$2
assert_is_directory() {
    if [[ ! -d $1 ]]; then
        die "$(printf '%q is not a directory' "$1")" 1
    fi
}
assert_is_directory "$SOURCE"
mkdir -p -- "$TARGET"
printf '%q ' "$@"

# find GNU cp
declare CP LN
is_gnu_command() { "$1" --version &>/dev/null; }
find_gnu_command() {
    declare -n VAR=${1^^}
    local i
    for i in "$1" g"$1"; do
        if is_gnu_command "$i"; then
            VAR=$i
            return 0;
        fi
    done
    die "Cannot find GNU $1"
}
find_gnu_command cp
find_gnu_command ln

is_nolink() {
    local needle=$1 i
    for i in "${nolink[@]}"; do
        if [[ $needle == */$i ]]; then
            return 0;
        fi
    done
    return 1
}

trouble() {
    local ret=$?
    if ((ret > 0)); then
        log 0 "Trouble -- $1 returned $ret."
    fi
}

shopt -s dotglob nullglob
for i in "$SOURCE"/*; do
    basename="${i#*/}"
    if is_nolink "$i"; then
        log 1 "Copying $basename..."
        # When on Windows, try replacing --reflink=auto with -l. A bit unsafe tho.
        "$CP" -a --reflink=auto -t "$TARGET" -- "$i"
        trouble "$CP" 
    else
        log 1 "Symlinking $basename..."
        "$LN" -rsf -t "$TARGET" -- "$i"
        trouble "$LN"
    fi
done
log 0 "Done, I think! Check your mods, delete old ones and stuff."