Allow use of --imply_local when calling DiffviewOpen, allowing LSP use and linting in MR review (#162)

Adds the ability to use the local filesystem when doing reviews by passing the `--imply-local` flag to the reviewer. This functionality is disabled by default. If users make changes to their filesystem (the files are "dirty") the default reviewer (hashes not files) will be use. This is a MINOR release.

lua/gitlab/reviewer/diffview.lua

@@ -9,6 +9,12 @@ local M = {
   tabnr = nil,
 }
 
+local all_git_manged_files_unmodified = function()
+  -- check local managed files are unmodified, matching the state in the MR
+  -- TODO: ensure correct CWD?
+  return vim.fn.trim(vim.fn.system({ "git", "status", "--short", "--untracked-files=no" })) == ""
+end
+
 M.open = function()
   local diff_refs = state.INFO.diff_refs
   if diff_refs == nil then
@@ -21,9 +27,25 @@ M.open = function()
     return
   end
 
-  vim.api.nvim_command(string.format("DiffviewOpen %s..%s", diff_refs.base_sha, diff_refs.head_sha))
+  local diffview_open_command = "DiffviewOpen"
+  local diffview_feature_imply_local = {
+    user_requested = state.settings.reviewer_settings.diffview.imply_local,
+    usable = all_git_manged_files_unmodified(),
+  }
+  if diffview_feature_imply_local.user_requested and diffview_feature_imply_local.usable then
+    diffview_open_command = diffview_open_command .. " --imply-local"
+  end
+
+  vim.api.nvim_command(string.format("%s %s..%s", diffview_open_command, diff_refs.base_sha, diff_refs.head_sha))
   M.tabnr = vim.api.nvim_get_current_tabpage()
 
+  if diffview_feature_imply_local.user_requested and not diffview_feature_imply_local.usable then
+    u.notify(
+      "There are uncommited changes in the working tree, cannot use 'imply_local' setting for gitlab reviews. Stash or commit all changes to use.",
+      vim.log.levels.WARN
+    )
+  end
+
   if state.INFO.has_conflicts then
     u.notify("This merge request has conflicts!", vim.log.levels.WARN)
   end