[READY] Do not send ultisnips snippets on every BufVisit

[bstaletic]

PR Prelude

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Please complete these steps and check these boxes (by putting an x inside the brackets) before filing your PR:

• [x] I have read and understood YCM's CONTRIBUTING document.
• [x] I have read and understood YCM's CODE_OF_CONDUCT document.
• [x] I have included tests for the changes in my PR. If not, I have included a rationale for why I haven't.
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Why this change is necessary and useful

[Please explain in detail why the changes in this PR are needed.]

Currently YCM gathers and passes snippets on every BufVisit, which seems wasteful. This pull request proposes a change of that, however it means that adding new snippets while editing won't be picked up when that buffer is revisited.

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This change is 

[codecov[bot]]

Codecov Report

Merging #3787 (bc83b01) into master (d52a4b3) will decrease coverage by 2.90%. The diff coverage is 16.66%.

@@            Coverage Diff             @@
##           master    #3787      +/-   ##
==========================================
- Coverage   91.19%   88.28%   -2.91%     
==========================================
  Files          26       23       -3     
  Lines        3258     2280     -978     
==========================================
- Hits         2971     2013     -958     
+ Misses        287      267      -20     

[bstaletic]

For the record, I made this pull request well after midnight. I might have done something stupid.

[bstaletic]

[mergify[bot]]

Thanks for sending a PR!

[puremourning]

@mergify refresh

[mergify[bot]]

Command refresh: success

Pull request refreshed

Hey, I reacted but my real name is @Mergifyio

[puremourning]

OK sure, no rush.

[bstaletic]

I can't get the test for this thing to work. @puremourning, either we close this or you'll have to get your hands dirty.

[puremourning]

I may pick this up in future, as it is a worthwhile performance help (I use a similar hack locally to improve perf). But for now, let's close this as it's unlikely to be merged as is.