fix(vcs): Make git_repo_base_ref return ref

CHANGELOG.md

@@ -9,7 +9,7 @@
 
 ### Fixes
 
-- Fix autofilled git base metadata (`--base-ref`, `--base-sha`) when using the `build upload` subcommand in git repos. Previously this worked only in the contexts of GitHub workflows ([#2897](https://github.com/getsentry/sentry-cli/pull/2897)).
+- Fix autofilled git base metadata (`--base-ref`, `--base-sha`) when using the `build upload` subcommand in git repos. Previously this worked only in the contexts of GitHub workflows ([#2897](https://github.com/getsentry/sentry-cli/pull/2897), [#2898](https://github.com/getsentry/sentry-cli/pull/2898)).
 
 ## 2.57.0
 

src/utils/vcs.rs

@@ -272,30 +272,26 @@ pub fn git_repo_head_ref(repo: &git2::Repository) -> Result<String> {
 }
 
 pub fn git_repo_base_ref(repo: &git2::Repository, remote_name: &str) -> Result<String> {
-    // Get the current HEAD commit
-    let head_commit = repo.head()?.peel_to_commit()?;
-
-    // Try to find the remote tracking branch
     let remote_branch_name = format!("refs/remotes/{remote_name}/HEAD");
     let remote_ref = repo.find_reference(&remote_branch_name).map_err(|e| {
         anyhow::anyhow!("Could not find remote tracking branch for {remote_name}: {e}")
     })?;
 
-    find_merge_base_ref(repo, &head_commit, &remote_ref)
-}
+    let name = remote_ref
+        .resolve()?
+        .shorthand()
+        .ok_or(anyhow::anyhow!("Remote branch name is not valid UTF-8"))?
+        .to_owned();
 
-fn find_merge_base_ref(
-    repo: &git2::Repository,
-    head_commit: &git2::Commit,
-    remote_ref: &git2::Reference,
-) -> Result<String> {
-    let remote_commit = remote_ref.peel_to_commit()?;
-    let merge_base_oid = repo.merge_base(head_commit.id(), remote_commit.id())?;
-
-    // Return the merge-base commit SHA as the base reference
-    let merge_base_sha = merge_base_oid.to_string();
-    debug!("Found merge-base commit as base reference: {merge_base_sha}");
-    Ok(merge_base_sha)
+    let expected_prefix = format!("{remote_name}/");
+    name.strip_prefix(&expected_prefix)
+        .map(|s| s.to_owned())
+        .ok_or_else(|| {
+            anyhow::anyhow!(
+                "Remote branch name '{name}' does not start with expected prefix \
+                '{expected_prefix}'"
+            )
+        })
 }
 
 /// Like git_repo_base_repo_name but preserves the original case of the repository name.