[gnome-builder] git: begin switch_branch implementation

[Christian Hergert <chergert src gnome org>]

commit 7c9b451d856dc672c94b2c4b4da2e62a1ba52726
Author: Christian Hergert <chergert redhat com>
Date:   Sun Jan 27 16:52:41 2019 -0800

    git: begin switch_branch implementation
    
    To do this well, we will need lots of fallbacks to handle situations where
    the contents are different. For now, we'll just set SAFE. However, in the
    future we should provide the user some choices in UI to browse the changes
    and select what to do. That should fit fine into the async/finish model
    since we can just delay the operation with a modal dialog.

 src/plugins/git/gbp-git-vcs.c | 100 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
---
diff --git a/src/plugins/git/gbp-git-vcs.c b/src/plugins/git/gbp-git-vcs.c
index 8dd963c93..5c0e7f92b 100644
--- a/src/plugins/git/gbp-git-vcs.c
+++ b/src/plugins/git/gbp-git-vcs.c
@@ -543,6 +543,104 @@ gbp_git_vcs_list_branches_finish (IdeVcs        *vcs,
   return ide_task_propagate_pointer (IDE_TASK (result), error);
 }
 
+static void
+gbp_git_vcs_switch_branch_worker (IdeTask      *task,
+                                  gpointer      source_object,
+                                  gpointer      task_data,
+                                  GCancellable *cancellable)
+{
+  g_autoptr(GgitCheckoutOptions) checkout_options = NULL;
+  g_autoptr(GgitObject) obj = NULL;
+  g_autoptr(GgitRef) ref = NULL;
+  g_autoptr(GError) error = NULL;
+  GbpGitVcs *self = source_object;
+  const gchar *id = task_data;
+
+  g_assert (IDE_IS_TASK (task));
+  g_assert (GBP_IS_GIT_VCS (self));
+  g_assert (id != NULL);
+  g_assert (!cancellable || G_IS_CANCELLABLE (cancellable));
+
+  ide_object_lock (IDE_OBJECT (self));
+
+  if (self->repository == NULL)
+    {
+      ide_task_return_new_error (task,
+                                 G_IO_ERROR,
+                                 G_IO_ERROR_FAILED,
+                                 "No repository to switch");
+      goto unlock;
+    }
+
+  if (!(ref = ggit_repository_lookup_reference (self->repository, id, &error)) ||
+      !(obj = ggit_ref_lookup (ref, &error)))
+    {
+      ide_task_return_error (task, g_steal_pointer (&error));
+      goto unlock;
+    }
+
+  checkout_options = ggit_checkout_options_new ();
+  ggit_checkout_options_set_strategy (checkout_options, GGIT_CHECKOUT_SAFE);
+
+  /* Update the tree contents */
+  if (!ggit_repository_checkout_tree (self->repository,
+                                      obj,
+                                      checkout_options,
+                                      &error))
+    {
+      ide_task_return_error (task, g_steal_pointer (&error));
+      goto unlock;
+    }
+
+  /* Now update head to point at the branch */
+  if (!ggit_repository_set_head (self->repository, id, &error))
+    {
+      ide_task_return_error (task, g_steal_pointer (&error));
+      goto unlock;
+    }
+
+  ide_task_return_boolean (task, TRUE);
+
+unlock:
+  ide_object_unlock (IDE_OBJECT (self));
+}
+
+static void
+gbp_git_vcs_switch_branch_async (IdeVcs              *vcs,
+                                 IdeVcsBranch        *branch,
+                                 GCancellable        *cancellable,
+                                 GAsyncReadyCallback  callback,
+                                 gpointer             user_data)
+{
+  g_autoptr(IdeTask) task = NULL;
+
+  g_assert (IDE_IS_MAIN_THREAD ());
+  g_assert (GBP_IS_GIT_VCS (vcs));
+  g_assert (GBP_IS_GIT_BRANCH (branch));
+  g_assert (!cancellable || G_IS_CANCELLABLE (cancellable));
+
+  task = ide_task_new (vcs, cancellable, callback, user_data);
+  ide_task_set_source_tag (task, gbp_git_vcs_switch_branch_async);
+  ide_task_set_task_data (task,
+                          g_strdup (ide_vcs_branch_get_name (branch)),
+                          g_free);
+  ide_task_run_in_thread (task, gbp_git_vcs_switch_branch_worker);
+}
+
+static gboolean
+gbp_git_vcs_switch_branch_finish (IdeVcs        *vcs,
+                                  GAsyncResult  *result,
+                                  GError       **error)
+{
+  g_assert (IDE_IS_MAIN_THREAD ());
+  g_assert (GBP_IS_GIT_VCS (vcs));
+  g_assert (IDE_IS_TASK (result));
+
+  ide_vcs_emit_changed (vcs);
+
+  return ide_task_propagate_boolean (IDE_TASK (result), error);
+}
+
 static void
 vcs_iface_init (IdeVcsInterface *iface)
 {
@@ -554,6 +652,8 @@ vcs_iface_init (IdeVcsInterface *iface)
   iface->list_status_finish = gbp_git_vcs_list_status_finish;
   iface->list_branches_async = gbp_git_vcs_list_branches_async;
   iface->list_branches_finish = gbp_git_vcs_list_branches_finish;
+  iface->switch_branch_async = gbp_git_vcs_switch_branch_async;
+  iface->switch_branch_finish = gbp_git_vcs_switch_branch_finish;
 }
 
 static void