[services] Add note sync service

Added service to automatically commit changes in notes directory (every
2 minutes) and automatically push them to their remote origin (after no
  changes occured for an hour).

Uses git and systemd to work as a service in the background. Gets
restarted on failure.

services/.config/systemd/user/commit_notes.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=Automatically commit notes in directory
+After=graphical.target
+
+[Service]
+Type=simple
+Environment=TIME_TO_COMMIT=120 UNCHANGED_RUNS_TO_PUSH=30
+ExecStart=/bin/bash -c '%h/.local/share/services/git-sync'
+Restart=on-failure
+
+[Install]
+WantedBy=multi-user.target

services/.local/share/services/git-sync

@@ -0,0 +1,71 @@
+#!/usr/bin/env sh
+
+# time in seconds to check for changes to commit
+TIME_TO_COMMIT=${GS_TIME_TO_COMMIT:-120}
+# amount of times to check for changes *without changes occurring* to push to origin
+UNCHANGED_RUNS_TO_PUSH=${GS_UNCHANGED_RUNS_TO_PUSH:-30}
+
+NOTEDIR=${WIKIROOT:-"$HOME/documents/notes"}/uni
+[ -z "$NOTEDIR" ] && [ -z "$1" ] && {
+  msg "ERROR: Please supply a directory to sync."
+  exit 1
+}
+
+DIR="${NOTEDIR:-$1}"
+
+commit() {
+  run_git pull --ff-only --ff
+
+  msg "Committing changes to $DIR"
+  run_git add .
+  # shellcheck disable=2039
+  run_git commit --no-gpg-sign -m "Git sync: $(date +%F_%R) from ${HOSTNAME:-"$HOST"}"
+}
+
+push() {
+  msg "No changes for $((UNCHANGED_RUNS_TO_PUSH * TIME_TO_COMMIT)) seconds, pushing to origin"
+  run_git push
+}
+
+should_commit() {
+  if [ "$(run_git status --porcelain | wc -l)" -eq 0 ]; then
+    msg "No changes to commit in $DIR"
+    false
+  fi
+  msg "Found changes to commit in $DIR"
+  true
+}
+
+should_push() {
+  if [ "$no_change_cycle" -ge "$UNCHANGED_RUNS_TO_PUSH" ]; then
+    true
+  else
+    false
+  fi
+}
+
+run_git() {
+  git -C "$DIR" "$@"
+}
+
+msg() {
+  echo "$1"
+}
+
+no_change_cycle=0
+while true; do
+  if should_commit; then
+    commit
+    no_change_cycle=0
+  fi
+
+  if should_push; then
+    push
+    no_change_cycle=-9999
+  fi
+
+  msg "No changes for $((no_change_cycle * TIME_TO_COMMIT)) of $((UNCHANGED_RUNS_TO_PUSH * TIME_TO_COMMIT)) seconds, going back to sleep for $((TIME_TO_COMMIT)) seconds."
+
+  no_change_cycle=$((no_change_cycle + 1))
+  sleep "$TIME_TO_COMMIT"
+done