Merge pull request #5869 from hardenedapple/undojoin-curhead

Don't set `b_u_curhead` in `ex_undojoin()`

test/functional/ex_cmds/undojoin_spec.lua

@@ -0,0 +1,38 @@
+local helpers = require('test.functional.helpers')(after_each)
+
+local eq = helpers.eq
+local clear = helpers.clear
+local insert = helpers.insert
+local feed = helpers.feed
+local expect = helpers.expect
+local execute = helpers.execute
+local exc_exec = helpers.exc_exec
+
+describe(':undojoin command', function()
+  before_each(function()
+    clear()
+    insert([[
+    Line of text 1
+    Line of text 2]])
+    execute('goto 1')
+  end)
+  it('joins changes in a buffer', function()
+    execute('undojoin | delete')
+    expect([[
+    Line of text 2]])
+    feed('u')
+    expect([[
+    ]])
+  end)
+  it('does not corrupt undolist when connected with redo', function()
+    feed('ixx<esc>')
+    execute('undojoin | redo')
+    expect([[
+    xxLine of text 1
+    Line of text 2]])
+  end)
+  it('does not raise an error when called twice', function()
+    local ret = exc_exec('undojoin | undojoin')
+    eq(0, ret)
+  end)
+end)