repository: remove log message override for switching the active branch

We want to use the "checkout: moving from ..." message in order to let
git know when a change of branch has happened. Make the convenience
functions for this goal write this message.

5 files changed, 72 insertions, 35 deletions

diff --git a/src/clone.c b/src/clone.c
index ac6a059dd..7e5d3302e 100644
--- a/src/clone.c
+++ b/src/clone.c
@@ -127,8 +127,7 @@ static int update_head_to_new_branch(
 
 	if (!error)
 		error = git_repository_set_head(
-			repo, git_reference_name(tracking_branch),
-			reflog_message);
+			repo, git_reference_name(tracking_branch));
 
 	git_reference_free(tracking_branch);
 
@@ -169,7 +168,7 @@ static int update_head_to_remote(
 	error = git_remote_default_branch(&branch, remote);
 	if (error == GIT_ENOTFOUND) {
 		error = git_repository_set_head_detached(
-			repo, remote_head_id, reflog_message);
+			repo, remote_head_id);
 		goto cleanup;
 	}
 
diff --git a/src/refs.c b/src/refs.c
index 415918600..3f6c33dcd 100644
--- a/src/refs.c
+++ b/src/refs.c
@@ -589,7 +589,7 @@ static int reference__rename(git_reference **out, git_reference *ref, const char
 
 	/* Update HEAD it was pointing to the reference being renamed */
 	if (should_head_be_updated &&
-		(error = git_repository_set_head(ref->db->repo, normalized, message)) < 0) {
+		(error = git_repository_set_head(ref->db->repo, normalized)) < 0) {
 		giterr_set(GITERR_REFERENCE, "Failed to update HEAD after renaming reference");
 		return error;
 	}
@@ -1284,10 +1284,8 @@ int git_reference_is_valid_name(const char *refname)
 	return git_reference__is_valid_name(refname, GIT_REF_FORMAT_ALLOW_ONELEVEL);
 }
 
-const char *git_reference_shorthand(const git_reference *ref)
+const char *git_reference__shorthand(const char *name)
 {
-	const char *name = ref->name;
-
 	if (!git__prefixcmp(name, GIT_REFS_HEADS_DIR))
 		return name + strlen(GIT_REFS_HEADS_DIR);
 	else if (!git__prefixcmp(name, GIT_REFS_TAGS_DIR))
@@ -1300,3 +1298,8 @@ const char *git_reference_shorthand(const git_reference *ref)
 	/* No shorthands are avaiable, so just return the name */
 	return name;
 }
+
+const char *git_reference_shorthand(const git_reference *ref)
+{
+	return git_reference__shorthand(ref->name);
+}
diff --git a/src/refs.h b/src/refs.h
index ace93e33b..f78ea06b0 100644
--- a/src/refs.h
+++ b/src/refs.h
@@ -74,6 +74,7 @@ int git_reference__is_valid_name(const char *refname, unsigned int flags);
 int git_reference__is_branch(const char *ref_name);
 int git_reference__is_remote(const char *ref_name);
 int git_reference__is_tag(const char *ref_name);
+const char *git_reference__shorthand(const char *name);
 
 /**
  * Lookup a reference by name and try to resolve to an OID.
diff --git a/src/repository.c b/src/repository.c
index f8a4d3e56..778cdefd7 100644
--- a/src/repository.c
+++ b/src/repository.c
@@ -1889,39 +1889,62 @@ cleanup:
 	return error;
 }
 
-static bool looks_like_a_branch(const char *refname)
+static int checkout_message(git_buf *out, git_reference *old, const char *new)
 {
-	return git__prefixcmp(refname, GIT_REFS_HEADS_DIR) == 0;
+	git_buf_puts(out, "checkout: moving from ");
+
+	if (git_reference_type(old) == GIT_REF_SYMBOLIC)
+		git_buf_puts(out, git_reference__shorthand(git_reference_symbolic_target(old)));
+	else
+		git_buf_puts(out, git_oid_tostr_s(git_reference_target(old)));
+
+	git_buf_puts(out, " to ");
+
+	if (git_reference__is_branch(new))
+		git_buf_puts(out, git_reference__shorthand(new));
+	else
+		git_buf_puts(out, new);
+
+	if (git_buf_oom(out))
+		return -1;
+
+	return 0;
 }
 
 int git_repository_set_head(
 	git_repository* repo,
-	const char* refname,
-	const char *log_message)
+	const char* refname)
 {
-	git_reference *ref,
-		*new_head = NULL;
+	git_reference *ref = NULL, *current = NULL, *new_head = NULL;
+	git_buf log_message = GIT_BUF_INIT;
 	int error;
 
 	assert(repo && refname);
 
+	if ((error = git_reference_lookup(&current, repo, GIT_HEAD_FILE)) < 0)
+		return error;
+
+	if ((error = checkout_message(&log_message, current, refname)) < 0)
+		goto cleanup;
+
 	error = git_reference_lookup(&ref, repo, refname);
 	if (error < 0 && error != GIT_ENOTFOUND)
-		return error;
+		goto cleanup;
 
 	if (!error) {
 		if (git_reference_is_branch(ref)) {
 			error = git_reference_symbolic_create(&new_head, repo, GIT_HEAD_FILE,
-					git_reference_name(ref), true, log_message);
+					git_reference_name(ref), true, git_buf_cstr(&log_message));
 		} else {
-			error = git_repository_set_head_detached(repo, git_reference_target(ref),
-					log_message);
+			error = git_repository_set_head_detached(repo, git_reference_target(ref));
 		}
-	} else if (looks_like_a_branch(refname)) {
+	} else if (git_reference__is_branch(refname)) {
 		error = git_reference_symbolic_create(&new_head, repo, GIT_HEAD_FILE, refname,
-				true, log_message);
+				true, git_buf_cstr(&log_message));
 	}
 
+cleanup:
+	git_reference_free(current);
 	git_reference_free(ref);
 	git_reference_free(new_head);
 	return error;
@@ -1929,55 +1952,66 @@ int git_repository_set_head(
 
 int git_repository_set_head_detached(
 	git_repository* repo,
-	const git_oid* commitish,
-	const char *log_message)
+	const git_oid* commitish)
 {
 	int error;
-	git_object *object,
-		*peeled = NULL;
-	git_reference *new_head = NULL;
+	git_buf log_message = GIT_BUF_INIT;
+	git_object *object = NULL, *peeled = NULL;
+	git_reference *new_head = NULL, *current = NULL;
 
 	assert(repo && commitish);
 
-	if ((error = git_object_lookup(&object, repo, commitish, GIT_OBJ_ANY)) < 0)
+	if ((error = git_reference_lookup(&current, repo, GIT_HEAD_FILE)) < 0)
 		return error;
 
+	if ((error = git_object_lookup(&object, repo, commitish, GIT_OBJ_ANY)) < 0)
+		goto cleanup;
+
 	if ((error = git_object_peel(&peeled, object, GIT_OBJ_COMMIT)) < 0)
 		goto cleanup;
 
-	error = git_reference_create(&new_head, repo, GIT_HEAD_FILE, git_object_id(peeled), true, log_message);
+	if ((error = checkout_message(&log_message, current, git_oid_tostr_s(git_object_id(peeled)))) < 0)
+		goto cleanup;
+
+	error = git_reference_create(&new_head, repo, GIT_HEAD_FILE, git_object_id(peeled), true, git_buf_cstr(&log_message));
 
 cleanup:
 	git_object_free(object);
 	git_object_free(peeled);
+	git_reference_free(current);
 	git_reference_free(new_head);
 	return error;
 }
 
-int git_repository_detach_head(
-	git_repository* repo,
-	const char *reflog_message)
+int git_repository_detach_head(git_repository* repo)
 {
-	git_reference *old_head = NULL,
-		*new_head = NULL;
+	git_reference *old_head = NULL,	*new_head = NULL, *current = NULL;
 	git_object *object = NULL;
+	git_buf log_message = GIT_BUF_INIT;
 	int error;
 
 	assert(repo);
 
-	if ((error = git_repository_head(&old_head, repo)) < 0)
+	if ((error = git_reference_lookup(&current, repo, GIT_HEAD_FILE)) < 0)
 		return error;
 
+	if ((error = git_repository_head(&old_head, repo)) < 0)
+		goto cleanup;
+
 	if ((error = git_object_lookup(&object, repo, git_reference_target(old_head), GIT_OBJ_COMMIT)) < 0)
 		goto cleanup;
 
+	if ((error = checkout_message(&log_message, current, git_oid_tostr_s(git_object_id(object)))) < 0)
+		goto cleanup;
+
 	error = git_reference_create(&new_head, repo, GIT_HEAD_FILE, git_reference_target(old_head),
-			1, reflog_message);
+			1, git_buf_cstr(&log_message));
 
 cleanup:
 	git_object_free(object);
 	git_reference_free(old_head);
 	git_reference_free(new_head);
+	git_reference_free(current);
 	return error;
 }
 
diff --git a/src/submodule.c b/src/submodule.c
index cba6c0f77..567ab748e 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -984,7 +984,7 @@ int git_submodule_update(git_submodule *sm, int init, git_submodule_update_optio
 		update_options.checkout_opts.checkout_strategy = update_options.clone_checkout_strategy;
 
 		if ((error = git_clone(&sub_repo, submodule_url, sm->path, &clone_options)) < 0 ||
-			(error = git_repository_set_head_detached(sub_repo, git_submodule_index_id(sm), NULL)) < 0 ||
+			(error = git_repository_set_head_detached(sub_repo, git_submodule_index_id(sm))) < 0 ||
 			(error = git_checkout_head(sub_repo, &update_options.checkout_opts)) != 0)
 			goto done;
 	} else {
@@ -996,7 +996,7 @@ int git_submodule_update(git_submodule *sm, int init, git_submodule_update_optio
 		if ((error = git_submodule_open(&sub_repo, sm)) < 0 ||
 			(error = git_object_lookup(&target_commit, sub_repo, git_submodule_index_id(sm), GIT_OBJ_COMMIT)) < 0 ||
 			(error = git_checkout_tree(sub_repo, target_commit, &update_options.checkout_opts)) != 0 ||
-			(error = git_repository_set_head_detached(sub_repo, git_submodule_index_id(sm), NULL)) < 0)
+			(error = git_repository_set_head_detached(sub_repo, git_submodule_index_id(sm))) < 0)
 			goto done;
 
 		/* Invalidate the wd flags as the workdir has been updated. */