refs: Introduce git_reference_set_target_with_log()

include/git2/refs.h

@@ -334,6 +334,29 @@ GIT_EXTERN(int) git_reference_set_target(
 	git_reference *ref,
 	const git_oid *id);
 
+/**
+ * Create a new reference with the same name as the given reference but a
+ * different OID target and update the reflog with a given message.
+ *
+ * The reference must be a direct reference, otherwise this will fail.
+ *
+ * The new reference will be written to disk, overwriting the given reference.
+ *
+ * @param out Pointer to the newly created reference
+ * @param ref The reference
+ * @param id The new target OID for the reference
+ * @param signature The identity that will used to populate the reflog entry
+ * @param log_message The one line long message that has to be appended
+ * to the reflog
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_reference_set_target_with_log(
+	git_reference **out,
+	git_reference *ref,
+	const git_oid *id,
+	const git_signature *signature,
+	const char *log_message);
+
 /**
  * Rename an existing reference.
  *

src/refs.c

@@ -480,21 +480,49 @@ int git_reference_symbolic_create_with_log(
 		ref_out, repo, name, NULL, target, force, signature, log_message);
 }
 
+static int ensure_is_an_updatable_direct_reference(git_reference *ref)
+{
+	if (ref->type == GIT_REF_OID)
+		return 0;
+
+	giterr_set(GITERR_REFERENCE, "Cannot set OID on symbolic reference");
+	return -1;
+}
+
 int git_reference_set_target(
 	git_reference **out,
 	git_reference *ref,
 	const git_oid *id)
 {
+	int error;
+
 	assert(out && ref && id);
 
-	if (ref->type != GIT_REF_OID) {
-		giterr_set(GITERR_REFERENCE, "Cannot set OID on symbolic reference");
-		return -1;
-	}
+	if ((error = ensure_is_an_updatable_direct_reference(ref)) < 0)
+		return error;
 
 	return git_reference_create(out, ref->db->repo, ref->name, id, 1);
 }
 
+int git_reference_set_target_with_log(
+	git_reference **out,
+	git_reference *ref,
+	const git_oid *id,
+	const git_signature *signature,
+	const char *log_message)
+{
+	int error;
+
+	assert(out && ref && id);
+	assert(signature && log_message);
+
+	if ((error = ensure_is_an_updatable_direct_reference(ref)) < 0)
+		return error;
+
+	return git_reference_create_with_log(
+		out, ref->db->repo, ref->name, id, 1, signature, log_message);
+}
+
 int git_reference_symbolic_set_target(
 	git_reference **out,
 	git_reference *ref,

tests/refs/settargetwithlog.c

@@ -0,0 +1,55 @@
+#include "clar_libgit2.h"
+
+#include "repository.h"
+#include "git2/reflog.h"
+#include "reflog.h"
+#include "ref_helpers.h"
+
+static const char *br2_tip = "a4a7dce85cf63874e984719f4fdd239f5145052f";
+static const char *master_tip = "a65fedf39aefe402d3bb6e24df4d4f5fe4547750";
+static const char *br2_name = "refs/heads/br2";
+
+static git_repository *g_repo;
+
+void test_refs_settargetwithlog__initialize(void)
+{
+   g_repo = cl_git_sandbox_init("testrepo.git");
+}
+
+void test_refs_settargetwithlog__cleanup(void)
+{
+   cl_git_sandbox_cleanup();
+}
+
+void test_refs_settargetwithlog__updating_a_direct_reference_adds_a_reflog_entry(void)
+{
+	git_reference *reference, *reference_out;
+	git_oid current_id, target_id;
+	git_signature *signature;
+	git_reflog *reflog;
+	const git_reflog_entry *entry;
+
+	const char *message = "You've been logged, mate!";
+
+	git_oid_fromstr(&current_id, br2_tip);
+	git_oid_fromstr(&target_id, master_tip);
+
+	cl_git_pass(git_reference_lookup(&reference, g_repo, br2_name));
+
+	cl_git_pass(git_signature_now(&signature, "foo", "foo@bar"));
+
+	cl_git_pass(git_reference_set_target_with_log(
+		&reference_out, reference, &target_id, signature, message));
+
+	cl_git_pass(git_reflog_read(&reflog, reference_out));
+
+	entry = git_reflog_entry_byindex(reflog, 0);
+	cl_assert(git_oid_cmp(&current_id, &entry->oid_old) == 0);
+	cl_assert(git_oid_cmp(&target_id, &entry->oid_cur) == 0);
+	cl_assert_equal_s(message, entry->msg);
+
+	git_reflog_free(reflog);
+	git_reference_free(reference_out);
+	git_reference_free(reference);
+	git_signature_free(signature);
+}