fix: fetching non-standard git refspecs on non-github repos

src/cargo/sources/git/source.rs

@@ -236,7 +236,9 @@ impl<'gctx> GitSource<'gctx> {
                 trace!("updating git source `{:?}`", self.remote);
 
                 let locked_rev = locked_rev.clone().into();
-                self.remote.checkout(&db_path, db, &locked_rev, self.gctx)?
+                let manifest_reference = self.source_id.git_reference().unwrap();
+                self.remote
+                    .checkout(&db_path, db, manifest_reference, &locked_rev, self.gctx)?
             }
         };
         Ok((db, actual_rev))

src/cargo/sources/git/utils.rs

@@ -109,13 +109,15 @@ impl GitRemote {
         &self,
         into: &Path,
         db: Option<GitDatabase>,
+        manifest_reference: &GitReference,
         reference: &GitReference,
         gctx: &GlobalContext,
     ) -> CargoResult<(GitDatabase, git2::Oid)> {
         if let Some(mut db) = db {
             fetch(
                 &mut db.repo,
                 self.url(),
+                manifest_reference,
                 reference,
                 gctx,
                 RemoteKind::GitDependency,
@@ -138,6 +140,7 @@ impl GitRemote {
         fetch(
             &mut repo,
             self.url(),
+            manifest_reference,
             reference,
             gctx,
             RemoteKind::GitDependency,
@@ -993,7 +996,8 @@ pub fn with_fetch_options(
 pub fn fetch(
     repo: &mut git2::Repository,
     remote_url: &str,
-    reference: &GitReference,
+    manifest_reference: &GitReference,
+    locked_reference: &GitReference,
     gctx: &GlobalContext,
     remote_kind: RemoteKind,
 ) -> CargoResult<()> {
@@ -1009,7 +1013,7 @@ pub fn fetch(
     // Flag to keep track if the rev is a full commit hash
     let mut fast_path_rev: bool = false;
 
-    let oid_to_fetch = match github_fast_path(repo, remote_url, reference, gctx) {
+    let oid_to_fetch = match github_fast_path(repo, remote_url, locked_reference, gctx) {
         Ok(FastPathRev::UpToDate) => return Ok(()),
         Ok(FastPathRev::NeedsFetch(rev)) => Some(rev),
         Ok(FastPathRev::Indeterminate) => None,
@@ -1030,7 +1034,7 @@ pub fn fetch(
     // The `+` symbol on the refspec means to allow a forced (fast-forward)
     // update which is needed if there is ever a force push that requires a
     // fast-forward.
-    match reference {
+    match locked_reference {
         // For branches and tags we can fetch simply one reference and copy it
         // locally, no need to fetch other branches/tags.
         GitReference::Branch(b) => {
@@ -1061,6 +1065,12 @@ pub fn fetch(
                 // The reason we write to `refs/remotes/origin/HEAD` is that it's of special significance
                 // when during `GitReference::resolve()`, but otherwise it shouldn't matter.
                 refspecs.push(format!("+{0}:refs/remotes/origin/HEAD", rev));
+            } else if let GitReference::Rev(rev) = manifest_reference
+                && rev.starts_with("refs/")
+            {
+                // If the lockfile has a commit. we can't directly fetch it (unless we're talking
+                // to GitHub), so we fetch the ref associated with it from the manifest.
+                refspecs.push(format!("+{0}:{0}", rev));
             } else {
                 // We don't know what the rev will point to. To handle this
                 // situation we fetch all branches and tags, and then we pray

src/cargo/sources/registry/remote.rs

@@ -387,6 +387,7 @@ impl<'gctx> RegistryData for RemoteRegistry<'gctx> {
             repo,
             url.as_str(),
             &self.index_git_ref,
+            &self.index_git_ref,
             self.gctx,
             RemoteKind::Registry,
         )

tests/testsuite/git.rs

@@ -249,10 +249,20 @@ fn cargo_compile_git_dep_pull_request() {
 
     // Make a reference in GitHub's pull request ref naming convention.
     let repo = git2::Repository::open(&git_project.root()).unwrap();
-    let oid = repo.refname_to_id("HEAD").unwrap();
-    let force = false;
     let log_message = "open pull request";
-    repo.reference("refs/pull/330/head", oid, force, log_message)
+    let parent = repo.head().unwrap().peel_to_commit().unwrap();
+    let author = repo.signature().unwrap();
+    let oid = repo
+        .commit(
+            None,
+            &author,
+            &author,
+            log_message,
+            &parent.tree().unwrap(),
+            &[&parent],
+        )
+        .unwrap();
+    repo.reference("refs/pull/330/head", oid, false, log_message)
         .unwrap();
 
     let project = project
@@ -290,6 +300,25 @@ fn cargo_compile_git_dep_pull_request() {
         .run();
 
     assert!(project.bin("foo").is_file());
+
+    // Delete the local cache, but keep the Cargo.lock to prevent regression
+    // of <https://github.com/rust-lang/cargo/issues/16767>
+    // This ensures we fetch the refs/pull/330/head spec explicitly, even
+    // if we have a locked commit.
+    paths::cargo_home().join("git").rm_rf();
+
+    project
+        .cargo("check")
+        .env("CARGO_NET_GIT_FETCH_WITH_CLI", "true")
+        .with_stderr_data(str![[r#"
+[UPDATING] git repository `[ROOTURL]/dep1`
+...
+[CHECKING] dep1 v0.5.0 ([ROOTURL]/dep1?rev=refs%2Fpull%2F330%2Fhead#[..])
+[CHECKING] foo v0.0.0 ([ROOT]/foo)
+[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
+
+"#]])
+        .run();
 }
 
 #[cargo_test]