src/common: Check disk space before copying files to "$system_dir"

Provide another cushion against accidentally including large files,
especially on the first run.

src/common.bash

@@ -569,9 +569,32 @@ BEGIN {
 
 	LogLeave # Reading file attributes
 
+	LogEnter 'Checking disk space...\n'
+	local -i i
+	local -i total_blocks=0
+	local -i tmp_block_size tmp_blocks_free
+	tmp_block_size=$(stat -f -c %S "$system_dir")
+	tmp_blocks_free=$(stat -f -c %f "$system_dir")
+	for ((i=0; i<${#found_files[*]}; i++))
+	do
+		local -i size="${found_file_sizes[$i]}"
+		local -i blocks=$(((size+tmp_block_size-1)/tmp_block_size)) # Count blocks
+		total_blocks+=$blocks
+		if (( total_blocks >= tmp_blocks_free ))
+		then
+			local file="${found_files[$i]}"
+			Log 'Copying file %s (%s bytes / %s blocks) to temporary storage would exhaust free space on %s (%s bytes / %s blocks).\n' \
+				"$(Color C "%q" "$file")" "$(Color G "$size")" "$(Color G "$blocks")" \
+				"$(Color C "%q" "$system_dir")" "$(Color G "$((tmp_blocks_free * tmp_block_size))")" "$(Color G "$tmp_blocks_free")"
+			Log 'Perhaps add %s (or a parent directory) to configuration to ignore it, or run with %s pointing at another location.\n' \
+				"$(Color Y "IgnorePath %q" "$(dirname "$file")"/'*')" "$(Color Y "TMPDIR")"
+			FatalError 'Refusing to proceed.\n'
+		fi
+	done
+	LogLeave
+
 	LogEnter 'Processing found files...\n'
 
-	local i
 	for ((i=0; i<${#found_files[*]}; i++))
 	do
 		Log '%s/%s...\r' "$(Color G "$i")" "$(Color G "${#found_files[*]}")"