Compiling latest fails with "failed to determine package fingerprint"

[rcorre]

I'm trying to install the latest (0efa820) on Ubuntu 24 by running cargo install --path helix-term --locked.

That fails with:

error: failed to compile `helix-term v25.1.1 (/home/rrc/src/helix/helix-term)`, intermediate artifacts can be found at `/home/rrc/src/helix/target`.
To reuse those artifacts with a future compilation, set the environment variable `CARGO_TARGET_DIR` to that path.

Caused by:
  failed to determine package fingerprint for build script for helix-loader v25.1.1 (/home/rrc/src/helix/helix-loader)

Caused by:
  failed to determine the most recently modified file in /home/rrc/src/helix/helix-loader

Caused by:
  failed to determine list of files in /home/rrc/src/helix/helix-loader

Caused by:
  failed to open git index at /home/rrc/src/helix/.git/

Caused by:
  invalid data in index - calculated checksum does not match expected; class=Index (10)

If I remove --locked, I get:

error: failed to compile `helix-term v25.1.1 (/home/rrc/src/helix/helix-term)`, intermediate artifacts can be found at `/home/rrc/src/helix/target`.
To reuse those artifacts with a future compilation, set the environment variable `CARGO_TARGET_DIR` to that path.

Caused by:
  package `litemap v0.7.5` cannot be built because it requires rustc 1.81 or newer, while the currently active rustc version is 1.76.0
  Either upgrade to rustc 1.81 or newer, or use
  cargo update [email protected] --precise ver
  where `ver` is the latest version of `litemap` supporting rustc 1.76.0

Eventually, I ran rustup override set 1.81, and then cargo install --path helix-term (without --locked) succeeded.
Anyone know what's going on here? I saw a few related cargo bugs like rust-lang/cargo#9881 but I wanted to raise this just in case it was a helix issue.

FWIW, cargo install --path helix-term --locked worked fine earlier today on an ArchLinux machine.