shell: implement draw_progress() as a convenience function

source/shell/Makefile

@@ -5,5 +5,6 @@ obj-y += source/shell/echo.o
 obj-y += source/shell/flash.o
 obj-y += source/shell/ftl.o
 obj-y += source/shell/mufs.o
+obj-y += source/shell/progress.o
 obj-y += source/shell/rtc.o
 obj-y += source/shell/version.o

source/shell/progress.c

@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+#define TERM_WIDTH 80
+
+void draw_progress(FILE *fp, unsigned long pos, unsigned long max)
+{
+	unsigned long head = (TERM_WIDTH - 2) * pos / max;
+	unsigned long i;
+
+	fputc('[', fp);
+
+	for (i = 0; i <= head; ++i)
+		fputc('#', fp);
+
+	for (; i < (TERM_WIDTH - 2); ++i)
+		fputc(' ', fp);
+
+	fputc(']', fp);
+
+	for (i = 0; i < TERM_WIDTH; ++i)
+		fputc('\b', fp);
+}