Fix #1870: Race condition with some virus scanners

Some virus scanners take out handles on files we are going to
rename, causing access errors and preventing the rename. Typically
this is short lived. Retry rather than erroring.

No feedback given at the moment, and depends on an unreleased
retry, so WIP...

Cargo.toml

@@ -55,6 +55,10 @@ wait-timeout = "0.2"
 walkdir = "2"
 xz2 = "0.1.3"
 
+[dependencies.retry]
+version = "0.4"
+default-features = false
+
 [target."cfg(windows)".dependencies]
 cc = "1"
 winreg = "0.6"
@@ -100,3 +104,6 @@ path = "src/cli/main.rs"
 [profile.release]
 lto = true
 codegen-units = 1
+
+[patch.crates-io]
+retry = { path = "../retry" }

src/utils/utils.rs

@@ -11,6 +11,9 @@ use std::path::{Path, PathBuf};
 use std::process::Command;
 use url::Url;
 
+use retry::{retry, OperationResult};
+use retry::delay::{Fibonacci, jitter};
+
 #[cfg(windows)]
 use winapi::shared::minwindef::DWORD;
 
@@ -651,7 +654,24 @@ pub fn toolchain_sort<T: AsRef<str>>(v: &mut Vec<T>) {
 }
 
 fn rename(name: &'static str, src: &Path, dest: &Path) -> Result<()> {
-    fs::rename(src, dest).chain_err(|| ErrorKind::RenamingFile {
+    // https://github.com/rust-lang/rustup.rs/issues/1870
+    // 21 fib steps from 1 sums to ~28 seconds, hopefully more than enough
+    // for our previous poor performance that avoided the race condition with
+    // McAfee and Norton.
+    retry(
+        Fibonacci::from_millis(1).map(jitter).take(21), || {
+            match fs::rename(src, dest) {
+                Ok(v) => OperationResult::Ok(v),
+                Err(e) => {
+                    match e.kind() {
+                        io::ErrorKind::PermissionDenied => OperationResult::Retry(e),
+                        _ => OperationResult::Err(e)
+                    }
+                }
+            }
+        }
+    )
+    .chain_err(|| ErrorKind::RenamingFile {
         name,
         src: PathBuf::from(src),
         dest: PathBuf::from(dest),