add `--ignore-rust-version` for `cargo install`

[ensc]

Problem

Subcommands like build allow to ignore the minimum rust version of dependencies by the --ignore-rust-version flag.

Because build is a step of cargo install, this flag should be available there too.

Proposed Solution

Index: cargo/src/bin/cargo/commands/install.rs
===================================================================
--- cargo.orig/src/bin/cargo/commands/install.rs
+++ cargo/src/bin/cargo/commands/install.rs
@@ -78,6 +78,7 @@ pub fn cli() -> App {
                 .conflicts_with_all(&["git", "path", "index"]),
         )
         .arg_message_format()
+        .arg_ignore_rust_version()
         .arg_timings()
         .after_help("Run `cargo help install` for more detailed information.\n")

Notes

No response

[weihanglo]

This seems good to have to me.

BTW, Could you provide some crates that fail to compile due to their rust-version being set?

[ensc]

BTW, Could you provide some crates that fail to compile due to their rust-version being set?

clap-4.0.x builds fine with RUSTC_BOOTSTRAP=1 and rust-1.59 (update to a newer version is not possible). But cargo install fails due to rust-version and binaries must be installed manually.

[weihanglo]

The Cargo team talked about this in today's triage meeting. This is likely just an oversight and wasn't intended to not add it. That is to say, we are open to a pull request for adding this flag for cargo install.

Note that this flag is designed for low-level or exceptional circumstances. It is not something expected people use regularly.