At the moment it doesn't make a big difference, because the vast majority of
callers create a list of todos themselves to completely replace what git came up
with. We're changing this in the following commits though, and then it's helpful
to preserve merges.
We already show "merge" todo entries when starting an interactive rebase with
--rebase-merges outside of lazygit. Changing the type of a merge entry to "pick"
or "edit" doesn't make sense and shouldn't be allowed. Earlier in this branch we
have started to show "update-ref" entries, these can't be changed either (they
can be moved, though).
You might argue that it should be possible to change them to "drop", but in the
case of "update-ref" this doesn't make sense either, because "drop" needs a Sha
and we don't have one here. Also, you would then be able to later change it back
to "pick", so we would have to remember that this isn't allowed for this
particular drop entry; that's messy, so just disallow all editing.
It used to work on the assumption that rebasing commits in lazygit's model
correspond one-to-one to lines in the git-rebase-todo file, which isn't
necessarily true (e.g. when users use "git rebase --edit-todo" at the custom
command prompt and add a "break" between lines).
This is useful when working with stacked branches, because you can now move
"pick" entries across an update-ref command and you can tell exactly which
branch the commit will end up in.
It's also useful to spot situations where the --update-refs option didn't work
as desired. For example, if you duplicate a branch and want to rebase only one
of the branches but not the other (maybe for testing); if you have
rebase.updateRefs=true in your git config, then rebasing one branch will move
the other branch along. To solve this we'll have to introduce a way to delete
the update-ref entry (maybe by hitting backspace?); this is out of scope for
this PR, so for now users will have to type "git rebase --edit-todo" into the
custom command prompt to sort this out.
We will also have to prevent users from trying to turn update-ref commands into
other commands like "pick" or "drop"; we'll do this later in this branch.
So far the algorithm worked on the assumption that the output of the "git show"
command corresponds one-to-one to the lines of the rebase-todo file. This
assumption doesn't hold once we start to include todo lines that don't have a
sha (like update-ref), or when the todo file contains multiple entries for the
same sha. This should never happen normally, but it can if users manually edit
the todo file and duplicate a line.
The main reason for doing this (besides the reasons given for Status in the
previous commit) is that it allows us to easily convert from TodoCommand to
Action and back. This will be needed later in the branch. Fortunately,
TodoCommand is one-based, so this allows us to add an ActionNone constant with
the value 0.
This is unrelated to the changes in this PR, but since we are doing the same
thing for the commit.Action field in the next commit, it makes sense to do it
for Status too for consistency. Modelling this as an enum feels more natural
than modelling it as a string, since there's a finite set of possible values.
And it saves a little bit of memory (not very much, since none of the strings
were heap-allocated, but still).
