Index: src/text.c
===================================================================
--- src/text.c	(revision 5095)
+++ src/text.c	(working copy)
@@ -367,7 +367,97 @@
  * mark is on, tabsize columns. */
 void do_unindent(void)
 {
-    do_indent(-tabsize);
+    bool modified = FALSE;
+    size_t line_len, i, m, last_indent, indent_len, tmp_indent, indent_diff;
+    filestruct *top, *bot, *f, *oldcur;
+    size_t top_x, bot_x, oldx;
+
+    assert(openfile->current != NULL && openfile->current->data != NULL);
+
+    /* If the mark is on, use all lines covered by the mark. */
+    if (openfile->mark_set) {
+        mark_order((const filestruct **)&top, &top_x,
+        (const filestruct **)&bot, &bot_x, NULL);
+    /* Otherwise, use the current line. */
+    } else {
+        top = openfile->current;
+        bot = top;
+    }
+
+    /* Go through each line of the text. */
+    for (f = top; f != bot->next; f = f->next) {
+
+        /* Measure the indentation of the line. */
+        line_len = strlen(f->data);
+        m = 0;
+        indent_len = 0;
+        last_indent = 0;
+        tmp_indent = 0;
+        for (i = 0; i < line_len; i++) {
+            if (f->data[i] == '\t') {
+                last_indent = tmp_indent;
+                tmp_indent = i + 1;
+                m = 0;
+                indent_len++;
+            } else if (f->data[i] == ' ') {
+                m++;
+                indent_len++;
+                if(m == tabsize) {
+                    last_indent = tmp_indent;
+                    tmp_indent = i + 1;
+                    m = 0;
+                }
+            } else {
+                /* The end of the indentation. */
+                break;
+            }
+        }
+
+        /* If there's no indentation on the line. Continue to
+         * the next line. */
+        if (indent_len == 0)
+            continue;
+
+        if (!modified) {
+            modified = TRUE;
+            add_undo(SPLIT_BEGIN);
+            oldcur = openfile->current;
+        }
+
+        /* Trick do_deletion to work on our current line instead of
+         * the open file's current line. */
+        openfile->current = f;
+
+        /* Move the cursor and start deleting. */
+        oldx = openfile->current_x;
+        openfile->current_x = indent_len;
+        indent_diff = indent_len - last_indent;
+        for (i = 0; i < indent_diff; i++) {
+            do_left();
+            do_deletion(BACK);
+        }
+
+        openfile->current_x = oldx;
+        if (openfile->current_x > last_indent &&
+                openfile->current_x > indent_diff) {
+            openfile->current_x -= indent_diff;
+        }
+
+    }
+
+    if (modified) {
+
+        add_undo(SPLIT_END);
+
+        /* Restore our current line. */
+        openfile->current = oldcur;
+
+        /* Mark the file as modified. */
+        set_modified();
+
+        /* Update the screen. */
+        edit_refresh_needed = TRUE;
+    }
 }
 
 #define redo_paste undo_cut