handle autowriteall the same as autowrite

[bhcleek]

Vim docs say that autowriteall implies autowrite, so make sure that
go#cmd#autowrite() has the same behavior when only one of either
autowrite or autowriteall is set.

[codecov-io]

Codecov Report

Merging #1653 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1653   +/-   ##
=======================================
  Coverage   21.73%   21.73%           
=======================================
  Files          53       53           
  Lines        4173     4173           
=======================================
  Hits          907      907           
  Misses       3266     3266

Flag	Coverage Δ
#nvim	16.89% <0%> (ø)	⬆️
#vim74	19.38% <100%> (ø)	⬆️
#vim80	20.6% <100%> (ø)	⬆️

Impacted Files	Coverage Δ
autoload/go/cmd.vim	5.73% <100%> (ø)	⬆️

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[fatih]

@bhcleek I'm not sure about this change. Maybe I don't want to enable autowriteall because I don't want it to save on :exit ? (this is what I do btw). So in that regard, I think go#cmd#autowrite() is correct that it only checksautowrite. Is there something I'm missing here?

[bhcleek]

@fatih Thanks for taking the time to review this tiny PR.

Like you, my vim is configured with autowrite and noautowriteall, but after reading the docs for autowriteall, and verifying some of vim's behaviors when it's configured with noautowrite and autowriteall, I realized that go#cmd#autowrite was incomplete.

• go#cmd#autowrite is called to make sure any unsaved changes in a buffer are saved before running a command like :GoVet if the user has set autowrite.
• When a user sets only autowriteall and not autowrite (e.g. set autowriteall, set noautowrite), vim will behave as if autowrite is set. From :help autowriteall:

Setting this option also implies that Vim behaves like 'autowrite' has been set.

• You can see for yourself that when autowriteall is set and autowrite is not, that moving to another buffer saves the changes before showing the next buffer.

All this PR does is make sure that vim-go saves the buffer using the same rules with respect to autowrite and autowriteall that vim itself applies.