cargo: retry git fetch (with CLI) when failure is spurious

Mark `git fetch` (in the `CARGO_NET_GIT_FETCH_WITH_CLI` path) as a
command whose failure may be considered spurious, and enable retry logic
when such a failure occurs. This helps reduce intermittent errors in
situations where `git fetch` fails due to transient network or server
issues.

Author: BiagioFesta

src/cargo/sources/git/utils.rs

@@ -6,7 +6,7 @@ use crate::sources::git::fetch::RemoteKind;
 use crate::sources::git::oxide;
 use crate::sources::git::oxide::cargo_config_to_gitoxide_overrides;
 use crate::util::HumanBytes;
-use crate::util::errors::CargoResult;
+use crate::util::errors::{CargoResult, GitCliError};
 use crate::util::{GlobalContext, IntoUrl, MetricsCounter, Progress, network};
 use anyhow::{Context as _, anyhow};
 use cargo_util::{ProcessBuilder, paths};
@@ -1110,7 +1110,11 @@ fn fetch_with_cli(
         .cwd(repo.path());
     gctx.shell()
         .verbose(|s| s.status("Running", &cmd.to_string()))?;
-    cmd.exec()?;
+    network::retry::with_retry(gctx, || {
+        cmd.exec()
+            .map_err(|error| GitCliError::new(error, true).into())
+    })?;
+
     Ok(())
 }
 

src/cargo/util/errors.rs

@@ -338,6 +338,46 @@ impl From<std::io::Error> for CliError {
     }
 }
 
+// =============================================================================
+// Git CLI errors
+
+pub type GitCliResult = Result<(), GitCliError>;
+
+/// An error that occurred while invoking the `git` command-line tool.
+///
+/// This is used for errors from Git operations performed via CLI.
+/// It wraps a lower-level error and indicates whether the failure
+/// should be considered *spurious*.
+///
+/// Spurious failures might involve retry mechanism.
+#[derive(Debug)]
+pub struct GitCliError {
+    inner: Error,
+    is_spurious: bool,
+}
+
+impl GitCliError {
+    pub fn new(inner: Error, is_spurious: bool) -> GitCliError {
+        GitCliError { inner, is_spurious }
+    }
+
+    pub fn is_spurious(&self) -> bool {
+        self.is_spurious
+    }
+}
+
+impl std::error::Error for GitCliError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        self.inner.source()
+    }
+}
+
+impl fmt::Display for GitCliError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.inner.fmt(f)
+    }
+}
+
 // =============================================================================
 // Construction helpers
 

src/cargo/util/network/retry.rs

@@ -41,7 +41,7 @@
 //! - <https://en.wikipedia.org/wiki/Exponential_backoff>
 //! - <https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Retry-After>
 
-use crate::util::errors::HttpNotSuccessful;
+use crate::util::errors::{GitCliError, HttpNotSuccessful};
 use crate::{CargoResult, GlobalContext};
 use anyhow::Error;
 use rand::Rng;
@@ -223,6 +223,12 @@ fn maybe_spurious(err: &Error) -> bool {
         }
     }
 
+    if let Some(err) = err.downcast_ref::<GitCliError>() {
+        if err.is_spurious() {
+            return true;
+        }
+    }
+
     false
 }
 
@@ -402,3 +408,12 @@ fn retry_after_parsing() {
         _ => panic!("unexpected non-retry"),
     }
 }
+
+#[test]
+fn git_cli_error_spurious() {
+    let error = GitCliError::new(Error::msg("test-git-cli-error"), false);
+    assert!(!maybe_spurious(&error.into()));
+
+    let error = GitCliError::new(Error::msg("test-git-cli-error"), true);
+    assert!(maybe_spurious(&error.into()));
+}