Mega-sync from `rust-lang/rust`
This essentially implements `@oli-obk's` suggestion here https://github.com/rust-lang/rust-analyzer/pull/13459#issuecomment-1297285607, with `@eddyb's` help.
This PR is equivalent to 14 syncs (back and forth) between `rust-lang/rust` and `rust-lang/rust-analyzer`.
Working from this list (from bottom to top):
```
(x) a2a1d9954 ⬆️ rust-analyzer
(x) 79923c382 ⬆️ rust-analyzer
(x) c60b1f641 ⬆️ rust-analyzer
(x) 8807fc4cc ⬆️ rust-analyzer
(x) a99a48e78 ⬆️ rust-analyzer
(x) 4f55ebbd4 ⬆️ rust-analyzer
(x) f5fde4df4 ⬆️ rust-analyzer
(x) 459bbb422 ⬆️ rust-analyzer
(x) 65e1dc4d9 ⬆️ rust-analyzer
(x) 3e358a682 ⬆️ rust-analyzer
(x) 31519bb39 ⬆️ rust-analyzer
(x) 8231fee46 ⬆️ rust-analyzer
(x) 22c8c9c40 ⬆️ rust-analyzer
(x) 9d2cb42a4 ⬆️ rust-analyzer
```
(This listed was assembled by doing a `git subtree push`, which made a branch, and looking at the new commits in that branch, picking only those that were `⬆️ rust-analyzer` commits)
We used the following commands to simulate merges in both directions:
```shell
TO_MERGE=22c8c9c40 # taken from the list above, bottom to top
git merge --no-edit --no-ff $TO_MERGE
git merge --no-edit --no-ff $(git -C ../rust log --pretty=format:'%cN | %s | %ad => %P' | rg -m1 -F "$(git show --no-patch --pretty=format:%ad $TO_MERGE)" | tee /dev/stderr | rg '.* => \S+ (\S+)$' --replace '$1')
```
We encountered no merge conflicts that Git wasn't able to solve by doing it this way.
Here's what the commit graph looks like (as shown in the Git Lens VSCode extension):
<img width="1345" alt="image" src="https://user-images.githubusercontent.com/7998310/203984523-7c1a690a-8224-416c-8015-ed6e49667066.png">
This PR closes#13459
## Does this unbreak `rust->ra` syncs?
Yes, here's how we tried:
In `rust-analyzer`:
* check out `subtree-fix` (this PR's branch)
* make a new branch off of it: `git checkout -b subtree-fix-merge-test`
* simulate this PR getting merged with `git merge master`
In `rust`:
* pull latest master
* make a new branch: `git checkout -b test-change`
* mess with rust-analyzer (I added a comment to `src/tools/rust-analyzer/Cargo.toml`)
* commit
* run `git subtree push -P src/tools/rust-analyzer ra-local final-sync` (this follows the [Clippy sync guide](https://doc.rust-lang.org/nightly/clippy/development/infrastructure/sync.html))
This created a `final-sync` branch in `rust-analyzer`.
In `rust-analyzer`:
* `git merge --no-ff final-sync` (this follows the [Clippy sync guide](https://doc.rust-lang.org/nightly/clippy/development/infrastructure/sync.html))
Now `git log` in `rust-analyzer` shows this:
```
commit 460128387e46ddfc2b95921b2d7f6e913a3d2b9f (HEAD -> subtree-fix-merge-test)
Merge: 0513fc02a 9ce6a734f
Author: Amos Wenger <amoswenger@gmail.com>
Date: Fri Nov 25 13:28:24 2022 +0100
Merge branch 'final-sync' into subtree-fix-merge-test
commit 0513fc02a08ea9de952983624bd0a00e98044b36
Merge: 38c98d1ff 6918009fe
Author: Amos Wenger <amoswenger@gmail.com>
Date: Fri Nov 25 13:28:02 2022 +0100
Merge branch 'master' into subtree-fix-merge-test
commit 9ce6a734f37ef8e53689f1c6f427a9efafe846bd (final-sync)
Author: Amos Wenger <amoswenger@gmail.com>
Date: Fri Nov 25 13:26:26 2022 +0100
Mess with rust-analyzer just for fun
```
And `git diff 0513fc02a08ea9de952983624bd0a00e98044b36` shows this:
```patch
diff --git a/Cargo.toml b/Cargo.toml
index 286ef1e7d..c9e24cd19 100644
--- a/Cargo.toml
+++ b/Cargo.toml
`@@` -32,3 +32,5 `@@` debug = 0
# ungrammar = { path = "../ungrammar" }
# salsa = { path = "../salsa" }
+
+# lol, hi
```
## Does this unbreak `ra->rust` syncs?
Yes, here's how we tried.
From `rust`:
* `git checkout -b sync-from-ra`
* `git subtree pull -P src/tools/rust-analyzer ra-local subtree-fix-merge-test` (this is adapted from the [Clippy sync guide](https://doc.rust-lang.org/nightly/clippy/development/infrastructure/sync.html#performing-the-sync-from-clippy-to-rust-langrust), you would normally use `ra-upstream master` but we're simulating things here)
A commit editor pops up, there was no merge conflicts.
## How do we prevent this from happening again?
Like `@bjorn3` said in https://github.com/rust-lang/rust-analyzer/pull/13459#issuecomment-1293587848
> Whenever syncing from rust-analyzer -> rust you have to immediately sync the merge commit from rust -> rust-analyzer to prevent merge conflicts in the future.
But if we get it wrong again, at least now we have a not-so-painful way to fix it.
b651646510
