git-sync: Add sanity check before remote pull

Added check to fetch remote updates before actually pulling in remote
changes.
This may help somewhat with the modification of files when they are
simultaneously open in vim, though I am not entirely sure.
Needs further investigation.

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

@@ -19,13 +19,16 @@ set_target() {
   DIR="${GS_TARGETDIR:-$1}"
 }
 
-commit() {
+pull() {
+  msg "Pulling upstream changes into $DIR"
   run_git pull --ff-only --ff
+}
 
+commit() {
   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"}"
+  run_git commit --no-gpg-sign -m "Git sync: $(date +%F_%R) from ${HOSTNAME:-"${HOST:-undefined}"}"
 }
 
 push() {
@@ -38,7 +41,7 @@ should_commit() {
     msg "No changes to commit in $DIR" 2
     false
   else
-    msg "Found changes to commit in $DIR"
+    msg "Found changes to commit in $DIR" 2
     true
   fi
 }
@@ -51,12 +54,23 @@ should_push() {
   fi
 }
 
+should_pull() {
+  run_git fetch
+  # shellcheck disable=1083
+  if [ "$(run_git rev-parse HEAD)" = "$(run_git rev-parse @{u})" ]; then
+    false
+  else
+    true
+  fi
+}
+
 run_git() {
   git -C "$DIR" "$@"
 }
 
 # echos its first argument
 # verbosity level optionally set through second argument
+# default verbosity 1 (info), can be set to 2 (debug), or 0 (error)
 msg() {
   lvl=${2:-1}
   [ "$lvl" -gt "$VERBOSITY" ] && return 0
@@ -67,6 +81,10 @@ msg() {
 watch_changes() {
   no_change_cycle=0
   while true; do
+    if should_pull; then
+      pull
+    fi
+
     if should_commit; then
       commit
       no_change_cycle=0