Range diff picker omits the current branch when opened from status view

Description

The range diff ref picker omits the current branch when opened from the status view with d → r. HEAD is available and points to the same commit, but the branch name itself is absent.

Tested with Neogit v3.0.0-219-g37e0f22a (37e0f22a2345bad1bffe01b31970885882f46275).

Neovim version

NVIM v0.12.3
Build type: Release
LuaJIT 2.1.1774638290

Operating system and version

macOS 26.6 (25G72)

Steps to reproduce

1. Create a repository with main and check out a branch named feature.
2. Start Neovim in that repository with nvim -nu minimal.lua.
3. Run :Neogit.
4. Press d, then r.
5. Inspect the Diff for range from choices.

Expected behavior

feature is offered as a range endpoint.

Actual behavior

The choices include main and HEAD, but not feature.

Minimal config

vim.opt.runtimepath = { vim.env.VIMRUNTIME }

local root = vim.fn.fnamemodify(
  debug.getinfo(1, "S").source:sub(2),
  ":p:h"
) .. "/.min/plugins/"

local plugins = {
  plenary = "https://github.com/nvim-lua/plenary.nvim.git",
  diffview = "https://github.com/sindrets/diffview.nvim",
  neogit = "https://github.com/NeogitOrg/neogit",
}

vim.fn.mkdir(root, "p")

for name, url in pairs(plugins) do
  local path = root .. name

  if not vim.uv.fs_stat(path) then
    vim.fn.system({ "git", "clone", "--depth=1", url, path })
    assert(vim.v.shell_error == 0, "Failed to clone " .. name)
  end

  vim.opt.runtimepath:append(path)
end

require("neogit").setup({})

Additional context

The range action constructs its first candidate list as { commit, git.branch.current() or "HEAD" }. From the status view, commit is nil. Because util.merge uses ipairs, iteration stops before reaching the current branch at index 2. get_all_branches(false) also excludes the current branch, so no later candidate source adds it back.

• Range candidate construction
• util.merge implementation

Reproduce the status-view flow with d then r, then inspect lua/neogit/popups/diff/actions.lua around range candidate construction and lua/neogit/lib/util.lua around util.merge. Verify how a nil first candidate affects the merged choices and confirm the current branch is offered as a range endpoint when the issue is fixed.