Auto merge of rust-lang#2410 - rust-lang:miri_auto_ops, r=RalfJung

Some cleanups and docs around the auto ops

Author: bors

CONTRIBUTING.md

@@ -168,11 +168,15 @@ to `.vscode/settings.json` in your local Miri clone:
         "./cargo-miri/Cargo.toml"
     ],
     "rust-analyzer.checkOnSave.overrideCommand": [
+        "env",
+        "MIRI_AUTO_OPS=no",
         "./miri",
         "check",
         "--message-format=json"
     ],
     "rust-analyzer.buildScripts.overrideCommand": [
+        "env",
+        "MIRI_AUTO_OPS=no",
         "./miri",
         "check",
         "--message-format=json",

README.md

@@ -393,6 +393,9 @@ Some native rustc `-Z` flags are also very relevant for Miri:
 
 Moreover, Miri recognizes some environment variables:
 
+* `MIRI_AUTO_OPS` indicates whether the automatic execution of rustfmt, clippy and rustup-toolchain
+  should be skipped. If it is set to any value, they are skipped. This is used for avoiding
+  infinite recursion in `./miri` and to allow automated IDE actions to avoid the auto ops.
 * `MIRI_LOG`, `MIRI_BACKTRACE` control logging and backtrace printing during
   Miri executions, also [see "Testing the Miri driver" in `CONTRIBUTING.md`][testing-miri].
 * `MIRIFLAGS` (recognized by `cargo miri` and the test suite) defines extra

miri

@@ -53,8 +53,8 @@ EOF
 MIRIDIR=$(python3 -c 'import os, sys; print(os.path.dirname(os.path.realpath(sys.argv[1])))' "$0")
 
 ## Run the auto-things.
-if [ -z "$AUTO_OPS" ]; then
-    export AUTO_OPS=42
+if [ -z "$MIRI_AUTO_OPS" ]; then
+    export MIRI_AUTO_OPS=42
 
     # Run this first, so that the toolchain doesn't change after
     # other code has run.