Problem
- `redir_exec` is obsolete, but it keeps getting used in new tests
because people copy existing tests.
- Disadvantages of `redir_exec`:
- Captures extra junk before the actual error/message that we _want_ to test.
- Does not fail on error, unlike e.g. `command()`.
Solution
- Use new functions like `nvim_exec` and `pcall_err`.
mkfifo (msysgit) does not work outside of msys2 environment.
gzip tests fail on Windows.
mklink requires admin privs for file symbolic links so mklink fails.
Hope this will make people using feed_command less likely: this hides bugs.
Already found at least two:
1. msgpackparse() will show internal error: hash_add() in case of duplicate
keys, though it will still work correctly. Currently silenced.
2. ttimeoutlen was spelled incorrectly, resulting in option not being set when
expected. Test was still functioning somehow though. Currently fixed.
It is otherwise impossible to determine which test failed sanitizer/valgrind
check. test/functional/helpers.lua module return was changed so that tests which
do not provide after_each function to get new check will automatically fail.
When backupcopy=auto buf_write assumes backupcopy=yes when the file is a
hard/symbolic link. However this check was guarded by a UNIX ifdef. The
check itself is portable and the guard can be removed.
Added a couple tests to check the behaviour of bkc=auto and bkc=no
with a symbolic link.
Reported in #4525
