Wait for the sqlite3 process to terminate

When closing the pipe to sqlite3, the sqlite3 process is not terminated
instantly which leads to race conditions with Git in `histdb-sync`.
Therefore, this commit adds a block to wait for the sqlite3 process to
terminate in `_histdb_stop_sqlite_pipe`.

sqlite-history.zsh

@@ -15,6 +15,7 @@ else
 fi
 
 typeset -g HISTDB_INODE=""
+typeset -g HISTDB_SQLITE_PID=""
 typeset -g HISTDB_SESSION=""
 typeset -g HISTDB_HOST=""
 typeset -g HISTDB_INSTALLED_IN="${(%):-%N}"
@@ -36,14 +37,13 @@ _histdb_stop_sqlite_pipe () {
             exec {HISTDB_FD}>&-;  # https://stackoverflow.com/a/22794374/2639190
         fi
     fi
-    # Sometimes, it seems like closing the fd does not terminate the
-    # sqlite batch process, so here is a horrible fallback.
-    # if [[ -n $HISTDB_SQLITE_PID ]]; then
-    #     ps -o args= -p $HISTDB_SQLITE_PID | read -r args
-    #     if [[ $args == "sqlite3 -batch ${HISTDB_FILE}" ]]; then
-    #         kill -TERM $HISTDB_SQLITE_PID
-    #     fi
-    # fi
+    # Wait for the sqlite3 process to terminate
+    if [[ -n "${HISTDB_SQLITE_PID}" ]]; then
+        while ps -o pid= -p "${HISTDB_SQLITE_PID}" &>/dev/null; do
+            sleep 1
+        done
+        HISTDB_SQLITE_PID=""
+    fi
 }
 
 add-zsh-hook zshexit _histdb_stop_sqlite_pipe
@@ -53,6 +53,7 @@ _histdb_start_sqlite_pipe () {
     setopt local_options no_notify no_monitor
     mkfifo $PIPE
     sqlite3 -batch -noheader "${HISTDB_FILE}" < $PIPE >/dev/null &|
+    HISTDB_SQLITE_PID=$!
     sysopen -w -o cloexec -u HISTDB_FD -- $PIPE
     command rm $PIPE
     zstat -A HISTDB_INODE +inode ${HISTDB_FILE}