refactor: Resolve Arg::multiple deprecation

Note: `cargo vendor --sync` did not use `multi_opt` and so it has both
multiple occurrences **and** multiple values.  If we want to deprecate
this, we'll need `unstable-grouped` to be stablized (or pin our clap
version) and ensure each group has only 1 value.

src/bin/cargo/cli.rs

@@ -479,8 +479,7 @@ See 'cargo help <command>' for more information on a specific command.\n",
                 .help("Unstable (nightly-only) flags to Cargo, see 'cargo -Z help' for details")
                 .short('Z')
                 .value_name("FLAG")
-                .multiple(true)
-                .number_of_values(1)
+                .multiple_occurrences(true)
                 .global(true),
         )
         .subcommands(commands::builtin())

src/bin/cargo/commands/bench.rs

@@ -13,7 +13,7 @@ pub fn cli() -> App {
         .arg(
             Arg::new("args")
                 .help("Arguments for the bench binary")
-                .multiple(true)
+                .multiple_values(true)
                 .last(true),
         )
         .arg_targets_all(

src/bin/cargo/commands/install.rs

@@ -8,7 +8,11 @@ pub fn cli() -> App {
     subcommand("install")
         .about("Install a Rust binary. Default location is $HOME/.cargo/bin")
         .arg_quiet()
-        .arg(Arg::new("crate").forbid_empty_values(true).multiple(true))
+        .arg(
+            Arg::new("crate")
+                .forbid_empty_values(true)
+                .multiple_values(true),
+        )
         .arg(
             opt("version", "Specify a version to install")
                 .alias("vers")

src/bin/cargo/commands/run.rs

@@ -11,7 +11,11 @@ pub fn cli() -> App {
         .setting(AppSettings::TrailingVarArg)
         .about("Run a binary or example of the local package")
         .arg_quiet()
-        .arg(Arg::new("args").allow_invalid_utf8(true).multiple(true))
+        .arg(
+            Arg::new("args")
+                .allow_invalid_utf8(true)
+                .multiple_values(true),
+        )
         .arg_targets_bin_example(
             "Name of the bin target to run",
             "Name of the example target to run",

src/bin/cargo/commands/rustc.rs

@@ -10,7 +10,7 @@ pub fn cli() -> App {
         .setting(AppSettings::TrailingVarArg)
         .about("Compile a package, and pass extra options to the compiler")
         .arg_quiet()
-        .arg(Arg::new("args").multiple(true).help("Rustc flags"))
+        .arg(Arg::new("args").multiple_values(true).help("Rustc flags"))
         .arg_package("Package to build")
         .arg_jobs()
         .arg_targets_all(

src/bin/cargo/commands/rustdoc.rs

@@ -7,7 +7,7 @@ pub fn cli() -> App {
         .setting(AppSettings::TrailingVarArg)
         .about("Build a package's documentation, using specified custom flags.")
         .arg_quiet()
-        .arg(Arg::new("args").multiple(true))
+        .arg(Arg::new("args").multiple_values(true))
         .arg(opt(
             "open",
             "Opens the docs in a browser after the operation",

src/bin/cargo/commands/search.rs

@@ -8,7 +8,7 @@ pub fn cli() -> App {
     subcommand("search")
         .about("Search packages in crates.io")
         .arg_quiet()
-        .arg(Arg::new("query").multiple(true))
+        .arg(Arg::new("query").multiple_values(true))
         .arg_index()
         .arg(
             opt(

src/bin/cargo/commands/test.rs

@@ -15,7 +15,7 @@ pub fn cli() -> App {
         .arg(
             Arg::new("args")
                 .help("Arguments for the test binary")
-                .multiple(true)
+                .multiple_values(true)
                 .last(true),
         )
         .arg(

src/bin/cargo/commands/uninstall.rs

@@ -6,7 +6,7 @@ pub fn cli() -> App {
     subcommand("uninstall")
         .about("Remove a Rust binary")
         .arg_quiet()
-        .arg(Arg::new("spec").multiple(true))
+        .arg(Arg::new("spec").multiple_values(true))
         .arg_package_spec_simple("Package to uninstall")
         .arg(multi_opt("bin", "NAME", "Only uninstall the binary NAME"))
         .arg(opt("root", "Directory to uninstall packages from").value_name("DIR"))

src/bin/cargo/commands/vendor.rs

@@ -24,7 +24,8 @@ pub fn cli() -> App {
                 .help("Additional `Cargo.toml` to sync and vendor")
                 .value_name("TOML")
                 .allow_invalid_utf8(true)
-                .multiple(true),
+                .multiple_occurrences(true)
+                .multiple_values(true),
         )
         .arg(
             Arg::new("respect-source-config")

src/cargo/util/command_prelude.rs

@@ -1,5 +1,3 @@
-#![allow(deprecated)]
-
 use crate::core::compiler::{BuildConfig, MessageFormat};
 use crate::core::resolver::CliFeatures;
 use crate::core::{Edition, Workspace};
@@ -264,20 +262,16 @@ pub fn optional_multi_opt(
 ) -> Arg<'static> {
     opt(name, help)
         .value_name(value_name)
-        .multiple(true)
+        .multiple_occurrences(true)
+        .multiple_values(true)
         .min_values(0)
         .number_of_values(1)
 }
 
 pub fn multi_opt(name: &'static str, value_name: &'static str, help: &'static str) -> Arg<'static> {
-    // Note that all `.multiple(true)` arguments in Cargo should specify
-    // `.number_of_values(1)` as well, so that `--foo val1 val2` is
-    // *not* parsed as `foo` with values ["val1", "val2"].
-    // `number_of_values` should become the default in clap 3.
     opt(name, help)
         .value_name(value_name)
-        .multiple(true)
-        .number_of_values(1)
+        .multiple_occurrences(true)
 }
 
 pub fn subcommand(name: &'static str) -> App {