Robustly handle folds during a :move command

In order to re-order marks according to the :move command, do_move()
uses mark_adjust() in a non-standard manner. The non-standard action is
that it moves some marks *past* other marks. This doesn't matter for
marks, but mark_adjust() calls foldMarkAdjust() which simply changes
fold starts and lengths and doesn't have enough information to know that
other folds have to be checked and reordered.

The array of folds for each window are assumed to be in order of
increasing line number, and if this gets broken some folds can get
"lost".

There has been a previous patch to avoid this problem by deleting and
recalculating all folds in the window, but this comes at the cost of
closing all folds when executing :move, and doesn't cover the case of
manual folds.
This patch adds a new function foldMoveRange() specifically for the
:move command that handles reordering folds as well as simply moving
them. Additionally, we allow calling mark_adjust_nofold() that does the
same as mark_adjust() but doesn't affect any fold array.

Calling mark_adjust_nofold() should be done in the same manner as
calling mark_adjust(), but according changes to the fold arrays must be
done seperately by the calling function.

vim-patch:8.0.0457
vim-patch:8.0.0459
vim-patch:8.0.0461
vim-patch:8.0.0465

5 files changed, 510 insertions, 22 deletions

diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 1b83677807..c560ff9210 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -756,14 +756,6 @@ int do_move(linenr_T line1, linenr_T line2, linenr_T dest)
   linenr_T num_lines;  // Num lines moved
   linenr_T last_line;  // Last line in file after adding new text
 
-  // Moving lines seems to corrupt the folds, delete folding info now
-  // and recreate it when finished.  Don't do this for manual folding, it
-  // would delete all folds.
-  bool isFolded = hasAnyFolding(curwin) && !foldmethodIsManual(curwin);
-  if (isFolded) {
-    deleteFoldRecurse(&curwin->w_folds);
-  }
-
   if (dest >= line1 && dest < line2) {
     EMSG(_("E134: Move lines into themselves"));
     return FAIL;
@@ -801,21 +793,29 @@ int do_move(linenr_T line1, linenr_T line2, linenr_T dest)
    * their final destination at the new text position -- webb
    */
   last_line = curbuf->b_ml.ml_line_count;
-  mark_adjust(line1, line2, last_line - line2, 0L);
-  changed_lines(last_line - num_lines + 1, 0, last_line + 1, num_lines);
+  mark_adjust_nofold(line1, line2, last_line - line2, 0L);
   if (dest >= line2) {
-    mark_adjust(line2 + 1, dest, -num_lines, 0L);
+    mark_adjust_nofold(line2 + 1, dest, -num_lines, 0L);
+    FOR_ALL_TAB_WINDOWS(tab, win) {
+      if (win->w_buffer == curbuf) {
+        foldMoveRange(&win->w_folds, line1, line2, dest);
+      }
+    }
     curbuf->b_op_start.lnum = dest - num_lines + 1;
     curbuf->b_op_end.lnum = dest;
   } else {
-    mark_adjust(dest + 1, line1 - 1, num_lines, 0L);
+    mark_adjust_nofold(dest + 1, line1 - 1, num_lines, 0L);
+    FOR_ALL_TAB_WINDOWS(tab, win) {
+      if (win->w_buffer == curbuf) {
+        foldMoveRange(&win->w_folds, dest + 1, line1 - 1, line2);
+      }
+    }
     curbuf->b_op_start.lnum = dest + 1;
     curbuf->b_op_end.lnum = dest + num_lines;
   }
   curbuf->b_op_start.col = curbuf->b_op_end.col = 0;
-  mark_adjust(last_line - num_lines + 1, last_line,
-      -(last_line - dest - extra), 0L);
-  changed_lines(last_line - num_lines + 1, 0, last_line + 1, -extra);
+  mark_adjust_nofold(last_line - num_lines + 1, last_line,
+                     -(last_line - dest - extra), 0L);
 
   /*
    * Now we delete the original text -- webb
@@ -851,11 +851,6 @@ int do_move(linenr_T line1, linenr_T line2, linenr_T dest)
     changed_lines(dest + 1, 0, line1 + num_lines, 0L);
   }
 
-  // recreate folds
-  if (isFolded) {
-    foldUpdateAll(curwin);
-  }
-
   return OK;
 }
 
diff --git a/src/nvim/fold.c b/src/nvim/fold.c
index 7c0283971e..e2d1b017b6 100644
--- a/src/nvim/fold.c
+++ b/src/nvim/fold.c
@@ -2597,6 +2597,154 @@ static void foldRemove(garray_T *gap, linenr_T top, linenr_T bot)
   }
 }
 
+// foldMoveRange() {{{2
+static void reverse_fold_order(garray_T *gap, size_t start, size_t end)
+{
+  for (; start < end; start++, end--) {
+    fold_T *left = (fold_T *)gap->ga_data + start;
+    fold_T *right = (fold_T *)gap->ga_data + end;
+    fold_T tmp = *left;
+    *left = *right;
+    *right = tmp;
+  }
+}
+
+// Move folds within the inclusive range "line1" to "line2" to after "dest"
+// require "line1" <= "line2" <= "dest"
+//
+// There are the following situations for the first fold at or below line1 - 1.
+//       1  2  3  4
+//       1  2  3  4
+// line1    2  3  4
+//          2  3  4  5  6  7
+// line2       3  4  5  6  7
+//             3  4     6  7  8  9
+// dest           4        7  8  9
+//                4        7  8    10
+//                4        7  8    10
+//
+// In the following descriptions, "moved" means moving in the buffer, *and* in
+// the fold array.
+// Meanwhile, "shifted" just means moving in the buffer.
+// 1. not changed
+// 2. truncated above line1
+// 3. length reduced by  line2 - line1, folds starting between the end of 3 and
+//    dest are truncated and shifted up
+// 4. internal folds moved (from [line1, line2] to dest)
+// 5. moved to dest.
+// 6. truncated below line2 and moved.
+// 7. length reduced by line2 - dest, folds starting between line2 and dest are
+//    removed, top is moved down by move_len.
+// 8. truncated below dest and shifted up.
+// 9. shifted up
+// 10. not changed
+static void truncate_fold(fold_T *fp, linenr_T end)
+{
+  // I want to stop *at here*, foldRemove() stops *above* top
+  end += 1;
+  foldRemove(&fp->fd_nested, end - fp->fd_top, MAXLNUM);
+  fp->fd_len = end - fp->fd_top;
+}
+
+#define fold_end(fp) ((fp)->fd_top + (fp)->fd_len - 1)
+#define valid_fold(fp, gap) ((fp) < ((fold_T *)(gap)->ga_data + (gap)->ga_len))
+#define fold_index(fp, gap) ((size_t)(fp - ((fold_T *)(gap)->ga_data)))
+void foldMoveRange(garray_T *gap, const linenr_T line1, const linenr_T line2,
+                   const linenr_T dest)
+{
+  fold_T *fp;
+  const linenr_T range_len = line2 - line1 + 1;
+  const linenr_T move_len = dest - line2;
+  const bool at_start = foldFind(gap, line1 - 1, &fp);
+
+  if (at_start) {
+    if (fold_end(fp) > dest) {
+      // Case 4 -- don't have to change this fold, but have to move nested
+      // folds.
+      foldMoveRange(&fp->fd_nested, line1 - fp->fd_top, line2 -
+                    fp->fd_top, dest - fp->fd_top);
+      return;
+    } else if (fold_end(fp) > line2) {
+      // Case 3 -- Remove nested folds between line1 and line2 & reduce the
+      // length of fold by "range_len".
+      // Folds after this one must be dealt with.
+      foldMarkAdjustRecurse(&fp->fd_nested, line1 - fp->fd_top,
+                            line2 - fp->fd_top, MAXLNUM, -range_len);
+      fp->fd_len -= range_len;
+    } else {
+      // Case 2 -- truncate fold *above* line1.
+      // Folds after this one must be dealt with.
+      truncate_fold(fp, line1 - 1);
+    }
+    // Look at the next fold, and treat that one as if it were the first after
+    // "line1" (because now it is).
+    fp = fp + 1;
+  }
+
+  if (!valid_fold(fp, gap) || fp->fd_top > dest) {
+    // No folds after "line1" and before "dest"
+    // Case 10.
+    return;
+  } else if (fp->fd_top > line2) {
+    for (; valid_fold(fp, gap) && fold_end(fp) <= dest; fp++) {
+      // Case 9. (for all case 9's) -- shift up.
+      fp->fd_top -= range_len;
+    }
+    if (valid_fold(fp, gap) && fp->fd_top <= dest) {
+      // Case 8. -- ensure truncated at dest, shift up
+      truncate_fold(fp, dest);
+      fp->fd_top -= range_len;
+    }
+    return;
+  } else if (fold_end(fp) > dest) {
+    // Case 7 -- remove nested folds and shrink
+    foldMarkAdjustRecurse(&fp->fd_nested, line2 + 1 - fp->fd_top,
+                          dest - fp->fd_top, MAXLNUM, -move_len);
+    fp->fd_len -= move_len;
+    fp->fd_top += move_len;
+    return;
+  }
+
+  // Case 5 or 6: changes rely on whether there are folds between the end of
+  // this fold and "dest".
+  size_t move_start = fold_index(fp, gap);
+  size_t move_end = 0, dest_index = 0;
+  for (; valid_fold(fp, gap) && fp->fd_top <= dest; fp++) {
+    if (fp->fd_top <= line2) {
+      // 5, or 6
+      if (fold_end(fp) > line2) {
+        // 6, truncate before moving
+        truncate_fold(fp, line2);
+      }
+      fp->fd_top += move_len;
+      continue;
+    }
+
+    // Record index of the first fold after the moved range.
+    if (move_end == 0) {
+      move_end = fold_index(fp, gap);
+    }
+
+    if (fold_end(fp) > dest) {
+      truncate_fold(fp, dest);
+    }
+
+    fp->fd_top -= range_len;
+  }
+  dest_index = fold_index(fp, gap);
+
+  // All folds are now correct, but they are not necessarily in the correct
+  // order.
+  // We have to swap folds in the range [move_end, dest_index) with those in
+  // the range [move_start, move_end).
+  reverse_fold_order(gap, move_start, dest_index - 1);
+  reverse_fold_order(gap, move_start, move_start + dest_index - move_end - 1);
+  reverse_fold_order(gap, move_start + dest_index - move_end, dest_index - 1);
+}
+#undef fold_end
+#undef valid_fold
+#undef fold_index
+
 /* foldMerge() {{{2 */
 /*
  * Merge two adjacent folds (and the nested ones in them).
diff --git a/src/nvim/mark.c b/src/nvim/mark.c
index 4e05845eb5..de2fdd7f13 100644
--- a/src/nvim/mark.c
+++ b/src/nvim/mark.c
@@ -887,6 +887,23 @@ void ex_changes(exarg_T *eap)
  */
 void mark_adjust(linenr_T line1, linenr_T line2, long amount, long amount_after)
 {
+  mark_adjust_internal(line1, line2, amount, amount_after, true);
+}
+
+// mark_adjust_nofold() does the same as mark_adjust() but without adjusting
+// folds in any way. Folds must be adjusted manually by the caller.
+// This is only useful when folds need to be moved in a way different to
+// calling foldMarkAdjust() with arguments line1, line2, amount, amount_after,
+// for an example of why this may be necessary, see do_move().
+void mark_adjust_nofold(linenr_T line1, linenr_T line2, long amount,
+                        long amount_after)
+{
+  mark_adjust_internal(line1, line2, amount, amount_after, false);
+}
+
+static void mark_adjust_internal(linenr_T line1, linenr_T line2, long amount,
+                                 long amount_after, bool adjust_folds)
+{
   int i;
   int fnum = curbuf->b_fnum;
   linenr_T    *lp;
@@ -1011,8 +1028,9 @@ void mark_adjust(linenr_T line1, linenr_T line2, long amount, long amount_after)
         }
       }
 
-      /* adjust folds */
-      foldMarkAdjust(win, line1, line2, amount, amount_after);
+      if (adjust_folds) {
+        foldMarkAdjust(win, line1, line2, amount, amount_after);
+      }
     }
   }
 
diff --git a/src/nvim/testdir/test_fold.vim b/src/nvim/testdir/test_fold.vim
index 7cb9faa75f..de07a05a2c 100644
--- a/src/nvim/testdir/test_fold.vim
+++ b/src/nvim/testdir/test_fold.vim
@@ -1,5 +1,9 @@
 " Test for folding
 
+func! PrepIndent(arg)
+  return [a:arg] + repeat(["\t".a:arg], 5)
+endfu
+
 func! Test_address_fold()
   new
   call setline(1, ['int FuncName() {/*{{{*/', 1, 2, 3, 4, 5, '}/*}}}*/',
@@ -128,3 +132,140 @@ func Test_manual_fold_with_filter()
   call assert_equal(['1', '2', '3', '4', '5', '6', '7', '8', '9'], getline(1, '$'))
   bwipe!
 endfunc
+
+func! Test_move_folds_around_manual()
+  new
+  let input = PrepIndent("a") + PrepIndent("b") + PrepIndent("c")
+  call setline(1, PrepIndent("a") + PrepIndent("b") + PrepIndent("c"))
+  let folds=[-1, 2, 2, 2, 2, 2, -1, 8, 8, 8, 8, 8, -1, 14, 14, 14, 14, 14]
+  " all folds closed
+  set foldenable foldlevel=0 fdm=indent
+  " needs a forced redraw
+  redraw!
+  set fdm=manual
+  call assert_equal(folds, map(range(1, line('$')), 'foldclosed(v:val)'))
+  call assert_equal(input, getline(1, '$'))
+  7,12m0
+  call assert_equal(PrepIndent("b") + PrepIndent("a") + PrepIndent("c"), getline(1, '$'))
+  call assert_equal(folds, map(range(1, line('$')), 'foldclosed(v:val)'))
+  10,12m0
+  call assert_equal(PrepIndent("a")[1:] + PrepIndent("b") + ["a"] +  PrepIndent("c"), getline(1, '$'))
+  call assert_equal([1, 1, 1, 1, 1, -1, 7, 7, 7, 7, 7, -1, -1, 14, 14, 14, 14, 14], map(range(1, line('$')), 'foldclosed(v:val)'))
+  " moving should not close the folds
+  %d
+  call setline(1, PrepIndent("a") + PrepIndent("b") + PrepIndent("c"))
+  set fdm=indent
+  redraw!
+  set fdm=manual
+  call cursor(2, 1)
+  %foldopen
+  7,12m0
+  let folds=repeat([-1], 18)
+  call assert_equal(PrepIndent("b") + PrepIndent("a") + PrepIndent("c"), getline(1, '$'))
+  call assert_equal(folds, map(range(1, line('$')), 'foldclosed(v:val)'))
+  norm! zM
+  " folds are not corrupted and all have been closed
+  call assert_equal([-1, 2, 2, 2, 2, 2, -1, 8, 8, 8, 8, 8, -1, 14, 14, 14, 14, 14], map(range(1, line('$')), 'foldclosed(v:val)'))
+  %d
+  call setline(1, ["a", "\tb", "\tc", "\td", "\te"])
+  set fdm=indent
+  redraw!
+  set fdm=manual
+  %foldopen
+  3m4
+  %foldclose
+  call assert_equal(["a", "\tb", "\td", "\tc", "\te"], getline(1, '$'))
+  call assert_equal([-1, 5, 5, 5, 5], map(range(1, line('$')), 'foldclosedend(v:val)'))
+  %d
+  call setline(1, ["a", "\tb", "\tc", "\td", "\te", "z", "\ty", "\tx", "\tw", "\tv"])
+  set fdm=indent foldlevel=0
+  set fdm=manual
+  %foldopen
+  3m1
+  %foldclose
+  call assert_equal(["a", "\tc", "\tb", "\td", "\te", "z", "\ty", "\tx", "\tw", "\tv"], getline(1, '$'))
+  call assert_equal(0, foldlevel(2))
+  call assert_equal(5, foldclosedend(3))
+  call assert_equal([-1, -1, 3, 3, 3, -1, 7, 7, 7, 7], map(range(1, line('$')), 'foldclosed(v:val)'))
+  2,6m$
+  %foldclose
+  call assert_equal(5, foldclosedend(2))
+  call assert_equal(0, foldlevel(6))
+  call assert_equal(9, foldclosedend(7))
+  call assert_equal([-1, 2, 2, 2, 2, -1, 7, 7, 7, -1], map(range(1, line('$')), 'foldclosed(v:val)'))
+  %d
+  " Ensure moving around the edges still works.
+  call setline(1, PrepIndent("a") + repeat(["a"], 3) + ["\ta"])
+  set fdm=indent foldlevel=0
+  set fdm=manual
+  %foldopen
+  6m$
+  " The first fold has been truncated to the 5'th line.
+  " Second fold has been moved up because the moved line is now below it.
+  call assert_equal([0, 1, 1, 1, 1, 0, 0, 0, 1, 0], map(range(1, line('$')), 'foldlevel(v:val)'))
+  bw!
+endfunc
+
+func! Test_move_folds_around_indent()
+  new
+  let input = PrepIndent("a") + PrepIndent("b") + PrepIndent("c")
+  call setline(1, PrepIndent("a") + PrepIndent("b") + PrepIndent("c"))
+  let folds=[-1, 2, 2, 2, 2, 2, -1, 8, 8, 8, 8, 8, -1, 14, 14, 14, 14, 14]
+  " all folds closed
+  set fdm=indent
+  call assert_equal(folds, map(range(1, line('$')), 'foldclosed(v:val)'))
+  call assert_equal(input, getline(1, '$'))
+  7,12m0
+  call assert_equal(PrepIndent("b") + PrepIndent("a") + PrepIndent("c"), getline(1, '$'))
+  call assert_equal(folds, map(range(1, line('$')), 'foldclosed(v:val)'))
+  10,12m0
+  call assert_equal(PrepIndent("a")[1:] + PrepIndent("b") + ["a"] +  PrepIndent("c"), getline(1, '$'))
+  call assert_equal([1, 1, 1, 1, 1, -1, 7, 7, 7, 7, 7, -1, -1, 14, 14, 14, 14, 14], map(range(1, line('$')), 'foldclosed(v:val)'))
+  " moving should not close the folds
+  %d
+  call setline(1, PrepIndent("a") + PrepIndent("b") + PrepIndent("c"))
+  set fdm=indent
+  call cursor(2, 1)
+  %foldopen
+  7,12m0
+  let folds=repeat([-1], 18)
+  call assert_equal(PrepIndent("b") + PrepIndent("a") + PrepIndent("c"), getline(1, '$'))
+  call assert_equal(folds, map(range(1, line('$')), 'foldclosed(v:val)'))
+  norm! zM
+  " folds are not corrupted and all have been closed
+  call assert_equal([-1, 2, 2, 2, 2, 2, -1, 8, 8, 8, 8, 8, -1, 14, 14, 14, 14, 14], map(range(1, line('$')), 'foldclosed(v:val)'))
+  %d
+  call setline(1, ["a", "\tb", "\tc", "\td", "\te"])
+  set fdm=indent
+  %foldopen
+  3m4
+  %foldclose
+  call assert_equal(["a", "\tb", "\td", "\tc", "\te"], getline(1, '$'))
+  call assert_equal([-1, 5, 5, 5, 5], map(range(1, line('$')), 'foldclosedend(v:val)'))
+  %d
+  call setline(1, ["a", "\tb", "\tc", "\td", "\te", "z", "\ty", "\tx", "\tw", "\tv"])
+  set fdm=indent foldlevel=0
+  %foldopen
+  3m1
+  %foldclose
+  call assert_equal(["a", "\tc", "\tb", "\td", "\te", "z", "\ty", "\tx", "\tw", "\tv"], getline(1, '$'))
+  call assert_equal(1, foldlevel(2))
+  call assert_equal(5, foldclosedend(3))
+  call assert_equal([-1, 2, 2, 2, 2, -1, 7, 7, 7, 7], map(range(1, line('$')), 'foldclosed(v:val)'))
+  2,6m$
+  %foldclose
+  call assert_equal(9, foldclosedend(2))
+  call assert_equal(1, foldlevel(6))
+  call assert_equal(9, foldclosedend(7))
+  call assert_equal([-1, 2, 2, 2, 2, 2, 2, 2, 2, -1], map(range(1, line('$')), 'foldclosed(v:val)'))
+  " Ensure moving around the edges still works.
+  %d
+  call setline(1, PrepIndent("a") + repeat(["a"], 3) + ["\ta"])
+  set fdm=indent foldlevel=0
+  %foldopen
+  6m$
+  " The first fold has been truncated to the 5'th line.
+  " Second fold has been moved up because the moved line is now below it.
+  call assert_equal([0, 1, 1, 1, 1, 0, 0, 0, 1, 1], map(range(1, line('$')), 'foldlevel(v:val)'))
+  bw!
+endfunc
diff --git a/test/functional/normal/fold_spec.lua b/test/functional/normal/fold_spec.lua
index a2a2a35a8b..5584db20ba 100644
--- a/test/functional/normal/fold_spec.lua
+++ b/test/functional/normal/fold_spec.lua
@@ -5,9 +5,13 @@ local insert = helpers.insert
 local feed = helpers.feed
 local expect = helpers.expect
 local execute = helpers.execute
+local funcs = helpers.funcs
+local foldlevel, foldclosedend = funcs.foldlevel, funcs.foldclosedend
+local eq = helpers.eq
 
 describe('Folds', function()
   clear()
+  before_each(function() execute('enew!') end)
   it('manual folding adjusts with filter', function()
     insert([[
     1
@@ -44,4 +48,186 @@ describe('Folds', function()
     8
     9]])
   end)
+  describe('adjusting folds after :move', function()
+    local function manually_fold_indent()
+      -- setting foldmethod twice is a trick to get vim to set the folds for me
+      execute('set foldmethod=indent', 'set foldmethod=manual')
+      -- Ensure that all folds will get closed (makes it easier to test the
+      -- length of folds).
+      execute('set foldminlines=0')
+      -- Start with all folds open (so :move ranges aren't affected by closed
+      -- folds).
+      execute('%foldopen!')
+    end
+
+    local function get_folds()
+      local rettab = {}
+      for i = 1, funcs.line('$') do
+        table.insert(rettab, foldlevel(i))
+      end
+      return rettab
+    end
+
+    local function test_move_indent(insert_string, move_command)
+      -- This test is easy because we just need to ensure that the resulting
+      -- fold is the same as calculated when creating folds from scratch.
+      insert(insert_string)
+      execute(move_command)
+      local after_move_folds = get_folds()
+      -- Doesn't change anything, but does call foldUpdateAll()
+      execute('set foldminlines=0')
+      eq(after_move_folds, get_folds())
+      -- Set up the buffer with insert_string for the manual fold testing.
+      execute('enew!')
+      insert(insert_string)
+      manually_fold_indent()
+      execute(move_command)
+    end
+
+    it('neither closes nor corrupts folds', function()
+      test_move_indent([[
+a
+	a
+	a
+	a
+	a
+	a
+a
+	a
+	a
+		a
+	a
+	a
+a
+	a
+	a
+	a
+	a
+	a]], '7,12m0')
+      expect([[
+a
+	a
+	a
+		a
+	a
+	a
+a
+	a
+	a
+	a
+	a
+	a
+a
+	a
+	a
+	a
+	a
+	a]])
+      -- lines are not closed, folds are correct
+      for i = 1,funcs.line('$') do
+        eq(-1, funcs.foldclosed(i))
+        if i == 1 or i == 7 or i == 13 then
+          eq(0, foldlevel(i))
+        elseif i == 4 then
+          eq(2, foldlevel(i))
+        else
+          eq(1, foldlevel(i))
+        end
+      end
+      -- folds are not corrupted
+      feed('zM')
+      eq(6, foldclosedend(2))
+      eq(12, foldclosedend(8))
+      eq(18, foldclosedend(14))
+    end)
+    it("doesn't split a fold when the move is within it", function()
+      test_move_indent([[
+a
+	a
+	a
+		a
+		a
+		a
+		a
+	a
+	a
+a]], '5m6')
+      eq({0, 1, 1, 2, 2, 2, 2, 1, 1, 0}, get_folds())
+    end)
+    it('truncates folds that end in the moved range', function()
+      test_move_indent([[
+a
+	a
+		a
+		a
+		a
+a
+a]], '4,5m6')
+      eq({0, 1, 2, 0, 0, 0, 0}, get_folds())
+    end)
+    it('moves folds that start between moved range and destination', function()
+      test_move_indent([[
+a
+	a
+	a
+	a
+	a
+a
+a
+	a
+		a
+	a
+a
+a
+	a]], '3,4m$')
+      eq({0, 1, 1, 0, 0, 1, 2, 1, 0, 0, 1, 0, 0}, get_folds())
+    end)
+    it('does not affect folds outside changed lines', function()
+      test_move_indent([[
+	a
+	a
+	a
+a
+a
+a
+	a
+	a
+	a]], '4m5')
+      eq({1, 1, 1, 0, 0, 0, 1, 1, 1}, get_folds())
+    end)
+    it('moves and truncates folds that start in moved range', function()
+      test_move_indent([[
+a
+	a
+		a
+		a
+		a
+a
+a
+a
+a
+a]], '1,3m7')
+      eq({0, 0, 0, 0, 0, 1, 2, 0, 0, 0}, get_folds())
+    end)
+    it('breaks a fold when moving text into it', function()
+      test_move_indent([[
+a
+	a
+		a
+		a
+		a
+a
+a]], '$m4')
+      eq({0, 1, 2, 2, 0, 0, 0}, get_folds())
+    end)
+    it('adjusts correctly when moving a range backwards', function()
+      test_move_indent([[
+a
+	a
+		a
+		a
+a]], '2,3m0')
+      eq({1, 2, 0, 0, 0}, get_folds())
+    end)
+  end)
 end)