Publish benchmarks to github pages

[matklad]

Deno has this swee:cake::cake::cake:eet page with benchmarks over here: https://deno.land/benchmarks.

I believe they are published automatically by travis: https://github.com/denoland/deno/blob/904c69c4c654e4b55fd2f46a063dc995cbe00e41/.travis.yml#L93

It would be tool to have something like this set up, though not pressing. Here's a great example for the benchmark: https://github.com/rust-analyzer/rust-analyzer/pull/489#discussion_r246931777

Here's the stuff we might want to measure:

• time to compile in release mode
• time to parse and validate parser.rs from rusct
• time to execute use std::collections::Hash completion

Technically, we should run benchmarking on master branch, as a cron-job.

[matklad]

This is how I imagine this should work:

• create an cargo xtask bench xtask.
• the task runs following times steps: rm target/release && cargo build -p rust-analyzer --release (bench compile time) git clone regex@some-sha (we want to pin some specific non-trivial non-huge benchmark target) rust-analyzer goto-definition (bench form scratch goto) rust-analyzer highlighiht (bench from scratych highlighitngin) ** rust-analyzer analysis-stats (bench typecheck)
• The results should be packaged into a JSON object

{
  "meta": { time: "${date}", sha1: "${git rev-parse HEAD}" , machine: "${OS, CPU, RAM}" },
  "measurements:" { "name": value }
}

• the JSON object is formatted into a single line and appended to https://github.com/rust-analyzer/benchmark-data/data.json
• the new commit is created against benchmark-data repository

Spearatelly, a /benchmarks page should be created on https://rust-analyzer.github.io/ to fetch and show this data with JavaScript.

[matklad]

fixed