Add git hook for package comparison

When moving to commit, this hook will automatically fire and check the
current system's installed packages against those explicitly committed
to the repository. If they mismatch it will inform the user.

It will not prevent the commit, but simply add a comment at the top of
the commit messages to remind the user that something is unbalanced
between both. It would be recommended to either check the additional
package into source control, remove it from the current system, or
explicitly add it to ignored packages.

.githooks/.stow-local-ignore

@@ -0,0 +1 @@
+^/.* # everything

.githooks/prepare-commit-msg

@@ -0,0 +1,58 @@
+#!/usr/bin/env sh
+
+COMMIT_MSG_FILE="$1"
+COMMIT_SOURCE="$2"
+
+pkgfileloc="$(git rev-parse --show-toplevel)/_bootstrap/packages.txt"
+pkgignoreloc="$(git rev-parse --show-toplevel)/_bootstrap/packages_ignore.txt"
+listgen="yay"
+
+err() {
+  printf "\x1b[33mCAUTION:\x1b[0m %s\n" "$*"
+  exit 1
+}
+
+if [ ! -f "$pkgfileloc" ]; then
+  err "File not found - $pkgfileloc, can not determine package differences!"
+fi
+
+if ! type "$listgen" >/dev/null 2>&1; then
+  err "Yay not installed on machine, can not reliably determine package differences!"
+fi
+
+# get commited packages, remove empty lines
+# and lines beginning with # to allow comments
+pkgcommited=$(mktemp)
+sed -e '/^[#$]/d' <"$pkgfileloc" | sort >"$pkgcommited"
+
+# get packages on this machine
+# q removes extraneous info
+# e only lists explicitly installed
+# tt removes those that are depended on, but NOT those optionally depended on
+pkgcurrent=$(yay -Qqett | sort)
+# remove those listed in package_ignore.txt
+if [ -f "$pkgignoreloc" ]; then
+  pkgcurrent=$(echo "$pkgcurrent" | comm -23 - "$pkgignoreloc")
+fi
+
+# compare the lists, list differences
+result=$(echo "$pkgcurrent" | comm -3 - "$pkgcommited")
+
+# get files only in repo (field1), and only on machine (field2)
+added=$(echo "$result" | cut -f1 | sed -e '/^$/d')
+removed=$(echo "$result" | cut -s -f2)
+
+# if we have no changes, do nothing
+if [ -n "$added" ] || [ -n "$removed" ]; then
+  text=$(printf "\-- PACKAGE DIFFERENCES TO COMMITED LIST FOUND --\nPackages NOT YET in repo:\n%s\n\nPackages ONLY in repo:%s\n" "$added" "$removed" | sed 's/^/# /gm')
+else
+  exit 0
+fi
+
+# prepend package changes to message
+case $COMMIT_SOURCE in
+"" | message, | template,)
+  msg=$(echo "$text" | cat - "$COMMIT_MSG_FILE")
+  printf "%s" "$msg" >"$COMMIT_MSG_FILE"
+  ;;
+esac

_bootstrap/.stow-local-ignore

@@ -1,4 +1,4 @@
 # TODO find a more generic way to express 'ignore any non-folder files'
 
 ^/install_packages.sh
-^/packages.csv
+^/packages.*.txt

install.sh

@@ -44,6 +44,19 @@ check_consent() {
   fi
 }
 
+enable_git_hooks() {
+  if [ "$1" == "false" ]; then
+    echo "Should we enable git hooks for this repository, so that installed packages are automatically compared when committing? [Y/n]"
+    read -r no
+    if [[ "$no" == n* ]]; then
+      echo "Not changing repository settings."
+      return
+    fi
+  fi
+  git config --local core.hooksPath .githooks/
+  echo "Changed repository settings."
+}
+
 install() {
   unattended=$1
   if ! "$unattended"; then
@@ -68,6 +81,9 @@ install() {
   # -- for some reason stow only works with unqoted var expansion
   stow -R ${targets} 2> >(grep -v 'Absolute/relative mismatch between Stow dir' 1>&2)
 
+  echo "================== ENABLING GIT REPOSITORY HOOKS =========================="
+  enable_git_hooks "$unattended"
+
   echo "====================== INSTALLATION FINISHED =============================="
   exit 0
 }