fix(node): validate git branch refs to close option injection

crates/gitlawb-node/src/api/mod.rs

@@ -92,6 +92,25 @@ pub(crate) fn require_repo_owner(record: &RepoRecord, caller: &str) -> Result<()
     }
 }
 
+/// Validate a branch name using the configured git binary (storage boundaries).
+pub(crate) fn validate_git_ref_with_git(
+    git_bin: &str,
+    name: &str,
+) -> std::result::Result<(), crate::git::store::GitRefValidationError> {
+    crate::git::store::validate_git_ref_with_git(git_bin, name)
+}
+
+/// Map ref-validation failures to the correct HTTP surface: malformed caller
+/// input stays 400; an inability to run git stays on the git/server-error path.
+pub(crate) fn map_git_ref_validation_error(
+    err: crate::git::store::GitRefValidationError,
+) -> AppError {
+    match err {
+        crate::git::store::GitRefValidationError::Invalid(msg) => AppError::BadRequest(msg),
+        crate::git::store::GitRefValidationError::GitUnavailable(msg) => AppError::Git(msg),
+    }
+}
+
 #[cfg(test)]
 mod did_tests {
     use super::did_matches;

crates/gitlawb-node/src/api/pulls.rs

@@ -50,6 +50,17 @@ pub async fn create_pr(
     let target_branch = req
         .target_branch
         .unwrap_or_else(|| record.default_branch.clone());
+
+    // Validate both refs before they are stored, since both are later
+    // interpolated into git argv (git diff / worktree add / merge). Validate the
+    // RESOLVED target, not just a caller-supplied one: create_repo also gates
+    // default_branch, but validating here as well means a PR can never feed the
+    // git sink an unchecked ref even if a default was poisoned by an older row
+    // or a future path that skips create_repo's gate.
+    crate::api::validate_git_ref_with_git(&state.git_bin, &req.source_branch)
+        .map_err(crate::api::map_git_ref_validation_error)?;
+    crate::api::validate_git_ref_with_git(&state.git_bin, &target_branch)
+        .map_err(crate::api::map_git_ref_validation_error)?;
     let number = state.db.next_pr_number(&record.id).await?;
     let now = Utc::now().to_rfc3339();
 

crates/gitlawb-node/src/api/repos.rs

@@ -242,6 +242,12 @@ pub async fn create_repo(
         ));
     }
 
+    // default_branch is caller-supplied and becomes a PR's target_branch when the
+    // PR omits one, which is interpolated into a git revision argument. Validate
+    // it as a ref so it cannot begin with '-' and inject a git option downstream.
+    crate::api::validate_git_ref_with_git(&state.git_bin, &req.default_branch)
+        .map_err(crate::api::map_git_ref_validation_error)?;
+
     // Owner is the authenticated agent's DID
     let owner_did = auth.0;