update-Makefiles

#!/bin/bash

kTHIS_NAME=$(basename "$BASH_SOURCE")
kTHIS_DIR=$(dirname "$BASH_SOURCE")
kTHIS_DIR_NAME=$(cd "$kTHIS_DIR" && basename "$PWD")

unset CDPATH  # to prevent unpredictable `cd` behavior

# Helper function for exiting with error message due to runtime error.
#   die [errMsg [exitCode]]
# Default error message states context and indicates that execution is aborted. Default exit code is 1.
# Prefix for context is always prepended.
# Note: An error message is *always* printed; if you just want to exit with a specific code silently, use `exit n` directly.
die() {
  echo "$kTHIS_NAME: ERROR: ${1:-"ABORTING due to unexpected error."}" 1>&2
  exit ${2:-1} # Note: If the argument is non-numeric, the shell prints a warning and uses exit code 255.
}

# Helper function for exiting with error message due to invalid arguments.
#   dieSyntax [errMsg]
# Default error message is provided, as is prefix and suffix; exit code is always 2.
dieSyntax() {
  echo "$kTHIS_NAME: ARGUMENT ERROR: ${1:-"Invalid argument(s) specified."} Use -h for help." 1>&2
  exit 2
}

# Regex for identifying Makefiles of the same type as this package's.
kMAKEFILE_ID_REGEX='^update-readme:'
kCUSTOM_MAKEFILE_REGEX='\[project-specific\]'

# Command-line help.
if [[ $1 == '--help' || $1 == '-h' ]]; then
  cat <<EOF
SYNOPSIS
  $kTHIS_NAME 

DESCRIPTION
  Updates Makefiles in this package's parent folder's subtree
  with the Makefile from this package, assuming:

  - they're not in hidden folders
  - they're not inside 'node_module' folders
  - they match a regex that identifies a Makefile as being
    an (older) copy of this package's:
       $kMAKEFILE_ID_REGEX
    while not also being marked as containing project-specific modifications
       $kCUSTOM_MAKEFILE_REGEX

  Note that no attempt is made to compare timestamps.

  You will be prompted for confirmation.

EOF
    exit 0
fi

# Make sure that not too many arguments were specified.
(( $# == 0 )) || dieSyntax "Unexpected argument(s) specified."

# Change to the folder in which this script resides.
cd "$kTHIS_DIR" || die

echo "== Looking for Makefiles to update, relative to ${PWD/#$HOME/~}..."

# Run the same command twice: 
#  - the first time to simply ECHO the copy commands that WOULD be performed if confirmed by prompt.
#  - the second time, if confirmed, to actually perform the copy commands.
cmdPrefix=( 'echo' '' )
for i in 0 1; do
  if (( i == 0 )); then
    # Read all candidate files into array ${files[@]}.
    IFS=$'\n' read -r -d '' -a files < <(find .. ! -path '../'"$kTHIS_DIR_NAME"'/*' ! -path '*/node_modules/*' ! -path '*/.*'  -name 'Makefile' -exec egrep -l "$kMAKEFILE_ID_REGEX" {} \;)
    # Read those we must exclude - those with project-specific modifications - into ${filesToExclude[@]}
    IFS=$'\n' read -r -d '' -a filesToExclude < <(egrep -l "$kCUSTOM_MAKEFILE_REGEX" "${files[@]}")
    if [[ -n $filesToExclude ]]; then
      cat <<EOF
===
WARNING: The following Makefiles are marked as having CUSTOM MODIFICATIONS 
         and will NOT be replaced - UPDATE THEM MANUALLY:

        ${filesToExclude[@]}
===    
EOF
      # Remove the files to exclude from ${files[@]}
      IFS=$'\n' read -r -d '' -a files < <(printf '%s\n' "${files[@]}" | grep -Fvx "$(printf '%s\n' "${filesToExclude[@]}")" )
    fi
  fi
  result=$(printf '%s\n' "${files[@]}" | xargs -I % ${cmdPrefix[i]} cp -p ./Makefile %) || die
  if (( i == 0 )); then
    [[ -n $result ]] || { die "No matching Makefiles found."; }
    echo "$result"
    while (( ! skipPrompt )); do
      read -p "== PERFORM COPY COMMANDS as stated above? (y/N) " promptInput
      [[ $promptInput =~ ^[yY]$ ]] && continue 2 # OK
      [[ $promptInput =~ ^[nN]$ || -z $promptInput ]] && { echo "Aborted." 1>&2; exit 1; }
      echo "Invalid input; please try again (^C to abort)." 1>&2
    done
    break
  else
    [[ -n $result ]] && echo $result
  fi
done
echo '== Done.'