lib/helpers: new functions _bash_it_history_auto_*()

Two new functions `_bash_it_history_auto_save()` and `_bash_it_history_auto_load()`, which append new history to disk and load new history from disk, respectively.

See Bash-it#1595 for discussion.

# Conflicts:
#	lib/helpers.bash
#	themes/base.theme.bash

lib/helpers.bash

@@ -952,6 +952,38 @@ function safe_append_preexec {
 	fi
 }
 
-function _save-and-reload-history() {
-	[[ ${autosave:-0} -eq 1 ]] && history -a && history -c && history -r
+function _bash_it_history_auto_save()
+{
+	case $HISTCONTROL in
+	*'noauto'*|*'autoload'*)
+		: # Do nothing, as configured.
+		;;
+	*'auto'*)
+		# Append new history from this session to the $HISTFILE
+		history -a
+		;;
+	*)
+		: # Do nothing, default.
+		;;
+	esac
+}
+
+function _bash_it_history_auto_load()
+{
+	case $HISTCONTROL in
+	*'noauto'*|*'autosave'*)
+		: # Do nothing, as configured.
+		;;
+	*'autoloadnew'*)
+		# Read new entries from $HISTFILE
+		history -n
+		;;
+	*'auto'*)
+		# Blank in-memory history, then read entire $HISTFILE fresh from disk.
+		history -c && history -r
+		;;
+	*)
+		: # Do nothing, default.
+		;;
+	esac
 }

themes/base.theme.bash

@@ -579,3 +579,46 @@ function aws_profile {
 		echo -e "default"
 	fi
 }
+
+function __check_precmd_conflict() {
+	local f
+	for f in "${precmd_functions[@]}"; do
+		if [[ "${f}" == "${1}" ]]; then
+			return 0
+		fi
+	done
+	return 1
+}
+
+function safe_append_prompt_command {
+	local prompt_re
+
+	if [ "${__bp_imported}" == "defined" ]; then
+		# We are using bash-preexec
+		if ! __check_precmd_conflict "${1}"; then
+			precmd_functions+=("${1}")
+		fi
+	else
+		# Set OS dependent exact match regular expression
+		if [[ ${OSTYPE} == darwin* ]]; then
+			# macOS
+			prompt_re="[[:<:]]${1}[[:>:]]"
+		else
+			# Linux, FreeBSD, etc.
+			prompt_re="\<${1}\>"
+		fi
+
+		if [[ ${PROMPT_COMMAND} =~ ${prompt_re} ]]; then
+			return
+		elif [[ -z ${PROMPT_COMMAND} ]]; then
+			PROMPT_COMMAND="${1}"
+		else
+			PROMPT_COMMAND="${1};${PROMPT_COMMAND}"
+		fi
+	fi
+}
+
+function _save-and-reload-history() {
+	[[ ${1:-${autosave:-${HISTORY_AUTOSAVE:-0}}} -eq 1 ]] && local HISTCONTROL="${HISTCONTROL:-}${HISTCONTROL:+:}autoshare"
+	_bash_it_history_auto_save && _bash_it_history_auto_load
+}