Add update_gitignore.sh helper command

ACE/bin/update_gitignore.sh

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+
+cmd="$1"
+if [[ "$cmd" == "help" ]] || [[ "$cmd" != "run" && "$cmd" != "dry-run" ]]
+then
+	if [[ "$cmd" != "help" ]]
+	then
+		echo "Error: Unrecognized command '$0 $1'"
+		echo ""
+	fi
+
+	echo "Usage:"
+	echo "  update_gitignore.sh run"
+	echo "  update_gitignore.sh dry-run"
+	echo ""
+	echo "This command finds all untracked and un-git-add-ed files in the repository and adds each file name to "
+	echo "a '.gitignore' file in the same directory. If a '.gitignore' file does not exist, one will be created. "
+	echo "Otherwise, the existing '.gitignore' file will be appended to. The 'dry-run' command enables you to "
+	echo "see a list of all detected file names that will be added to '.gitignore' files without making any "
+	echo "changes."
+	echo ""
+	echo "If the 'run' command does its job properly, running 'dry-run' immediately after should display no "
+	echo "planned actions."
+
+	if [[ "$cmd" == "help" ]]
+	then
+		exit 0
+	fi
+
+	exit 1
+fi
+
+export IFS=$'\n';
+
+for line in $(git status --short --untracked-files)
+do
+	if [[ $line == '??'* ]]
+	then
+		file="${line:3}"
+		d="$(dirname "${file}")"
+		f="$(basename "${file}")"
+
+		if [[ "$cmd" == "run" ]]
+		then
+			echo "Ignoring ${f} in ${d}/.gitignore"
+			echo "${f}" >> "${d}/.gitignore"
+		else
+			echo "Will ignore ${f} in ${d}/.gitignore"
+		fi
+	fi
+done