patch 8.0.0010
Problem:    Crash when editing file that starts with crypt yeader. (igor2x)
Solution:   Check for length of text. (Christian Brabandt) Add a test.
diff --git a/src/testdir/test_crypt.vim b/src/testdir/test_crypt.vim
new file mode 100644
index 0000000..10979dd
--- /dev/null
+++ b/src/testdir/test_crypt.vim
@@ -0,0 +1,42 @@
+" Tests for encryption.
+" TODO: include tests from test71.
+
+func Common_head_only(text)
+  " This was crashing Vim
+  split Xtest.txt
+  call setline(1, a:text)
+  wq
+  call feedkeys(":split Xtest.txt\<CR>foobar\<CR>", "tx")
+  call delete('Xtest.txt')
+  call assert_match('VimCrypt', getline(1))
+  bwipe!
+endfunc
+
+func Test_head_only_2()
+  call Common_head_only('VimCrypt~02!abc')
+endfunc
+
+func Test_head_only_3()
+  call Common_head_only('VimCrypt~03!abc')
+endfunc
+" Tests for encryption.
+" TODO: include tests from test71.
+
+func Common_head_only(text)
+  " This was crashing Vim
+  split Xtest.txt
+  call setline(1, a:text)
+  wq
+  call feedkeys(":split Xtest.txt\<CR>foobar\<CR>", "tx")
+  call delete('Xtest.txt')
+  call assert_match('VimCrypt', getline(1))
+  bwipe!
+endfunc
+
+func Test_head_only_2()
+  call Common_head_only('VimCrypt~02!abc')
+endfunc
+
+func Test_head_only_3()
+  call Common_head_only('VimCrypt~03!abc')
+endfunc