FEATURES:
0b5a7e4ad5ee #4432 API: external UIs can render custom popupmenu
c6ac4f84b163 #4934 API: call any API method from vimscript
31df051ed9a3 #4568 API: nvim_call_atomic(): multiple calls in a single request
b268ba353af4 #5424 API: nvim_win_get_number(), nvim_tabpage_get_number()
e7e2844d468d has("nvim-1.2.3") checks for a specific Nvim version
522b885a0db7 #5295, #5493 `:CheckHealth` checks tmux, terminfo, performance
719dae2e010c #5384 events: allow event processing in getchar()
f25797f86976 #5386 API: metadata: Nvim version & API level
22dfe6925d47 #5389 API: metadata: "since", "deprecated_since"
605e74327a40 Added QuickFixLine highlight group

CHANGES:
4af6ec746c82 #5253 perf: Disable clipboard in do_cmdline()
6e9f329d051c #5299 perf: Skip foldUpdate() in insert-mode.
9d4fcec7c6b6 #5426 perf: Do not auto-update folds for some foldmethods.
eeec0cab5848 #5419 tui: Default to normal-mode cursor shape.

FIXES:
e83845285cf3 #5436 tui: Fix "weird characters" / "bleeding termcodes"
10a54ad12e2d #5243 signal_init: Always unblock SIGCHLD.
bccb49bedb9b #5316 eval.c: Fix memory leak for detached pty job
626065d385c4 #5227 tchdir: New tab should inherit CWD.
cd321b7d0fb1 #5292 getcwd(): Return empty string if CWD is invalid.
6127eaef0534 shada: Fix non-writeable ShaDa directory handling
ca65514a241b #2789 system(): Respect shellxescape, shellxquote
2daf54ee8dd9 #4874 Restore vim-like tab dragging
0c536b5d8afe #5319 syntax.c: Support bg/fg special color-names.
3c53371b0ccb #4972 from justinmk/schedule-ui_refresh
68bcb32ec43e #4789 tui.c: Do not wait for tui loop on teardown.
c8b6ec2e6a85 #5409 v:count broken in command-line window
6bc3bcefc6ca #5461 fix emoji display
51937e1322de #5470 fix :terminal with :argadd, :argu
79d77da8a06b #5481 external UIs: opening multiple files from command-line
657ba62a84de #5501 rplugin: resolve paths in manifest file
6a6f188d2ac4 #5502 system('foo &', 'bar'): Show error, don't crash.
1ff162c0d99c #5515 os_nodetype: open fd with O_NONBLOCK
2a6c5bb0c4b0 #5450 modeline: Handle version number overflow.
0ade1bb7067d #5225 CI tests now run against Windows!

api: Nvim version + API level

API level is disconnected from NVIM version. The API metadata holds the
current API level, and the lowest backwards-compatible level supported
by this instance.

Release 0.1.6 is the first release that reports the Nvim version and API
level.

    metadata['version'] = {
      major: 0,
      minor: 1,
      patch: 6,
      api_level: 1,
      api_compatible: 0,
      api_prerelease: false,
    }

The API level may remain unchanged across Nvim releases if the API has
not changed.

When changing the API,
    - set NVIM_API_PRERELEASE to true
    - increment NVIM_API_LEVEL (at most once per Nvim version)
    - adjust NVIM_API_LEVEL_COMPAT if backwards-compatibility was broken

api_level_0.mpack was generated from Nvim 0.1.5 with:
    nvim --api-info

The API level is disconnected from the NVIM version. The API metadata
holds the current API level, and the lowest backwards-compatible level
supported by this instance.

Release 0.1.6 will be the first release reporting the Nvim version and
API level.

    metadata['version'] = {
      major: 0,
      minor: 1,
      patch: 6,
      prerelease: true,
      api_level: 1,
      api_compatible: 0,
    }

The API level may remain unchanged across Neovim releases if the API has
not changed.

When changing the API the CMake variable NVIM_API_PRERELEASE is set to
true, and  NVIM_API_CURRENT/NVIM_API_COMPATIBILITY are incremented
accordingly.

The functional tests check the API table against fixtures of past
versions of Neovim. It compares all the functions in the old table with
the new one, it does ignore some metadata attributes that do not alter
the function signature or were removed since 0.1.5.  Currently the only
fixture is 0.mpack, generated from Neovim 0.1.5 with nvim --api-info.

Closes #5246

Problem:    Memory leak when saving for undo fails.
Solution:   Free allocated memory. (Hirohito Higashi)

https://github.com/vim/vim/commit/1e2258297bb31720bfbeb234f2dae4d1b3b04fbd

Closes #5449

A file containing the string "vim" followed by a very large number in a modeline
location will trigger an overflow in getdigits() which is called by
chk_modeline() when trying to parse the version number.

Add getdigits_safe(), which does not assert overflows, but reports them to the
caller.

vim-patch:7.4.2109

Problem:    Setting 'display' to "lastline" is a drastic change, while
            omitting it results in lots of "@" lines.
Solution:   Add "truncate" to show "@@@" for a truncated line.

https://github.com/vim/vim/commit/ad9c2a08f0509294269a2f11a59a438b944bdd5a