Fix deleting update-ref todos

It is a bad idea to read a git-rebase-todo file, remove some update-ref todos,
and write it back out behind git's back. This will cause git to actually remove
the branches referenced by those update-ref todos when the rebase is continued.

The reason is that git remembers the refs affected by update-ref todos at the
beginning of the rebase, and remembers information about them in the file
.git/rebase-merge/update-refs. Then, whenever the user performs a "git rebase
--edit-todo" command, it updates that file based on whether update-ref todos
were added or removed by that edit. If we rewrite the git-rebase-todo file
behind git's back, this updating doesn't happen.

Fix this by not updating the git-rebase-todo file directly in this case, but
performing a "git rebase --edit-todo" command where we set ourselves as the
editor and change the file in there. This makes git update the bookkeeping
information properly.

Ideally we would use this method for all cases where we change the
git-rebase-todo file (e.g. moving todos up/down, or changing the type of a
todo); this would be cleaner because we wouldn't mess with git's private
implementation details. I tried this, but unfortunately it isn't fast enough.
Right now, moving a todo up or down takes between 1 and 2ms on my machine;
changing it to do a "git rebase --edit-todo" slows it down to over 100ms, which
is unacceptable.

1 files changed, 36 insertions, 1 deletions

diff --git a/pkg/commands/git_commands/rebase.go b/pkg/commands/git_commands/rebase.go
index 874cbd809..2d1de707f 100644
--- a/pkg/commands/git_commands/rebase.go
+++ b/pkg/commands/git_commands/rebase.go
@@ -250,6 +250,36 @@ func (self *RebaseCommands) PrepareInteractiveRebaseCommand(opts PrepareInteract
 	return cmdObj
 }
 
+// GitRebaseEditTodo runs "git rebase --edit-todo", saving the given todosFileContent to the file
+func (self *RebaseCommands) GitRebaseEditTodo(todosFileContent []byte) error {
+	ex := oscommands.GetLazygitPath()
+
+	cmdArgs := NewGitCmd("rebase").
+		Arg("--edit-todo").
+		ToArgv()
+
+	debug := "FALSE"
+	if self.Debug {
+		debug = "TRUE"
+	}
+
+	self.Log.WithField("command", cmdArgs).Debug("RunCommand")
+
+	cmdObj := self.cmd.New(cmdArgs)
+
+	cmdObj.AddEnvVars(daemon.ToEnvVars(daemon.NewWriteRebaseTodoInstruction(todosFileContent))...)
+
+	cmdObj.AddEnvVars(
+		"DEBUG="+debug,
+		"LANG=en_US.UTF-8",   // Force using EN as language
+		"LC_ALL=en_US.UTF-8", // Force using EN as language
+		"GIT_EDITOR="+ex,
+		"GIT_SEQUENCE_EDITOR="+ex,
+	)
+
+	return cmdObj.Run()
+}
+
 // AmendTo amends the given commit with whatever files are staged
 func (self *RebaseCommands) AmendTo(commits []*models.Commit, commitIndex int) error {
 	commit := commits[commitIndex]
@@ -302,11 +332,16 @@ func (self *RebaseCommands) DeleteUpdateRefTodos(commits []*models.Commit) error
 		return todoFromCommit(commit)
 	})
 
-	return utils.DeleteTodos(
+	todosFileContent, err := utils.DeleteTodos(
 		filepath.Join(self.repoPaths.WorktreeGitDirPath(), "rebase-merge/git-rebase-todo"),
 		todosToDelete,
 		self.config.GetCoreCommentChar(),
 	)
+	if err != nil {
+		return err
+	}
+
+	return self.GitRebaseEditTodo(todosFileContent)
 }
 
 func (self *RebaseCommands) MoveTodosDown(commits []*models.Commit) error {