Remove duplicate crate check.

[jdm]

Fixes #26262. We can always restore this check if we decide to disable dependabot or enforce keeping the list of duplicates up to date before merging the automated PRs.

[highfive]

Heads up! This PR modifies the following files:

• @wafflespeanut: python/tidy/servo_tidy_tests/test_tidy.py, python/tidy/servo_tidy/tidy.py

[SimonSapin]

I don’t think this is a good solution. Compiling Servo involves hundreds of crates. Without any automation to track duplicates I’m afraid this number could explode.

I think it’s fine to be more liberal about adding exceptions and allow duplicates, especially for security fixes. But I feel it’s still important to do so knowingly.

From the issue:

Dependabot removes duplicates by upgrading all dependencies step by step.

This would be true in a world where the entire ecosystem uses Dependabot. Duplicate crates are often due to an intermediate dependency (not in our repository) not having upgraded its own dependencies.

[jdm]

I'm going to start an email discussion about the future of dependabot usage and the duplicate crate check.

[Eijebong]

Here's what a full upgrade/update would look like 😱

./Cargo.lock:1: duplicate versions for package `wayland-protocols`
	The following packages depend on version 0.21.13 from 'crates.io':
	The following packages depend on version 0.23.6 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `winapi`
	The following packages depend on version 0.2.8 from 'crates.io':
	The following packages depend on version 0.3.8 from 'https://github.com/servo/winapi-rs?branch=patch-1':
./Cargo.lock:1: duplicate versions for package `cookie`
	The following packages depend on version 0.11.2 from 'crates.io':
	The following packages depend on version 0.12.0 from 'crates.io':
	The following packages depend on version 0.13.3 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `parking_lot_core`
	The following packages depend on version 0.6.2 from 'crates.io':
	The following packages depend on version 0.7.2 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `want`
	The following packages depend on version 0.2.0 from 'crates.io':
	The following packages depend on version 0.3.0 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `headers-core`
	The following packages depend on version 0.1.1 from 'crates.io':
	The following packages depend on version 0.2.0 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `winit`
	The following packages depend on version 0.19.3 from 'crates.io':
	The following packages depend on version 0.22.1 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `futures`
	The following packages depend on version 0.1.29 from 'crates.io':
	The following packages depend on version 0.3.4 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `smithay-client-toolkit`
	The following packages depend on version 0.4.6 from 'crates.io':
	The following packages depend on version 0.6.6 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `servo-fontconfig`
	The following packages depend on version 0.4.0 from 'crates.io':
	The following packages depend on version 0.5.0 from 'crates.io':
./Cargo.lock:1: duplicates for `peek-poke` are allowed, but only single version found
	The following packages depend on version 0.2.0 from 'https://github.com/servo/webrender':
./Cargo.lock:1: duplicate versions for package `png`
	The following packages depend on version 0.15.3 from 'crates.io':
	The following packages depend on version 0.16.3 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `headers`
	The following packages depend on version 0.2.3 from 'crates.io':
	The following packages depend on version 0.3.2 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `wayland-scanner`
	The following packages depend on version 0.21.13 from 'crates.io':
	The following packages depend on version 0.23.6 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `hyper`
	The following packages depend on version 0.12.35 from 'crates.io':
	The following packages depend on version 0.13.5 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `freetype`
	The following packages depend on version 0.4.1 from 'crates.io':
	The following packages depend on version 0.5.1 from 'crates.io':
./Cargo.lock:1: duplicates for `peek-poke-derive` are allowed, but only single version found
	The following packages depend on version 0.2.1 from 'https://github.com/servo/webrender':
./Cargo.lock:1: duplicate versions for package `bytes`
	The following packages depend on version 0.4.12 from 'crates.io':
	The following packages depend on version 0.5.4 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `libloading`
	The following packages depend on version 0.5.2 from 'crates.io':
	The following packages depend on version 0.6.1 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `tokio`
	The following packages depend on version 0.1.22 from 'crates.io':
	The following packages depend on version 0.2.19 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `http`
	The following packages depend on version 0.1.21 from 'crates.io':
	The following packages depend on version 0.2.1 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `deflate`
	The following packages depend on version 0.7.20 from 'crates.io':
	The following packages depend on version 0.8.4 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `nix`
	The following packages depend on version 0.14.1 from 'crates.io':
	The following packages depend on version 0.17.0 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `http-body`
	The following packages depend on version 0.1.0 from 'crates.io':
	The following packages depend on version 0.3.1 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `h2`
	The following packages depend on version 0.1.26 from 'crates.io':
	The following packages depend on version 0.2.4 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `wayland-client`
	The following packages depend on version 0.21.13 from 'crates.io':
	The following packages depend on version 0.23.6 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `rusttype`
	The following packages depend on version 0.7.9 from 'crates.io':
	The following packages depend on version 0.8.3 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `wayland-commons`
	The following packages depend on version 0.21.13 from 'crates.io':
	The following packages depend on version 0.23.6 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `servo-fontconfig-sys`
	The following packages depend on version 4.0.6 from 'crates.io':
	The following packages depend on version 5.0.1 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `time`
	The following packages depend on version 0.1.43 from 'crates.io':
	The following packages depend on version 0.2.10 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `parking_lot`
	The following packages depend on version 0.10.2 from 'crates.io':
	The following packages depend on version 0.9.0 from 'crates.io':

[eijebong@plutonium] ~/code/servo (nightly-2020-04-08) (master) >>> cat Cargo.lock | rg "name = " | awk '{ print $3 }' | sort | uniq -c | grep -v "1 \""
      2 "arrayvec"
      3 "base64"
      2 "bytes"
      2 "cocoa"
      3 "cookie"
      2 "core-foundation"
      2 "core-foundation-sys"
      2 "core-graphics"
      2 "core-text"
      2 "deflate"
      2 "dwrote"
      2 "freetype"
      2 "futures"
      3 "gleam"
      2 "gl_generator"
      2 "h2"
      2 "headers"
      2 "headers-core"
      2 "http"
      2 "http-body"
      2 "hyper"
      2 "libloading"
      2 "lyon_geom"
      2 "mio"
      2 "nix"
      2 "parking_lot"
      2 "parking_lot_core"
      2 "png"
      2 "proc-macro2"
      2 "quote"
      2 "rusttype"
      2 "servo-fontconfig"
      2 "servo-fontconfig-sys"
      2 "smallvec"
      2 "smithay-client-toolkit"
      2 "time"
      2 "tokio"
      2 "unicode-xid"
      2 "want"
      2 "wayland-client"
      2 "wayland-commons"
      2 "wayland-protocols"
      2 "wayland-scanner"
      3 "wayland-sys"
      2 "winapi"
      2 "winit"

[jdm]

Popular opinion seems to be against this.