bugfix: disable snacks animations in CodeDiff tabs

Fixes gitter with scrolling and commands like `gg` and `G`. See: https://github.com/esmuellert/codediff.nvim/issues/519

This config disables the snacks animations on CodeDiff tabs while
keeping them active in other tabs.

lua/plugins/codediff.lua

@@ -36,4 +36,52 @@ return {
     { "<leader>gl", ":'<,'>CodeDiff history<cr>", mode = "v", desc = "Toggle git log of selected lines" },
     { "<leader>gL", "<cmd>CodeDiff history<cr>", desc = "Toggle git log of current branch" },
   },
+  config = function(_, opts)
+    require("codediff").setup(opts)
+
+    -- Snacks' smooth scroll animates the scrolling codediff does to keep the two
+    -- panes in sync, so ]c/[c hunk navigation jitters (codediff.nvim#519).
+    -- Mute animations while a codediff tab is focused, restore on the way out.
+    -- Buffer-local vars can't scope this: the modified pane is the real file
+    -- buffer, so muting it would follow the file into other tabs.
+    local group = vim.api.nvim_create_augroup("codediff_snacks_animate", { clear = true })
+    local diff_tabs = {} ---@type table<integer, true>
+    local saved ---@type { value: boolean? }? set only while we are muting
+
+    local function sync_animations()
+      if diff_tabs[vim.api.nvim_get_current_tabpage()] then
+        -- Wrapped so an unset vim.g (the default, animations on) round-trips as
+        -- nil rather than reading as "nothing saved"
+        saved = saved or { value = vim.g.snacks_animate }
+        vim.g.snacks_animate = false
+      elseif saved then
+        vim.g.snacks_animate = saved.value
+        saved = nil
+      end
+    end
+
+    vim.api.nvim_create_autocmd("User", {
+      group = group,
+      pattern = "CodeDiffOpen",
+      callback = function(ev)
+        diff_tabs[ev.data.tabpage] = true
+        sync_animations()
+      end,
+    })
+
+    vim.api.nvim_create_autocmd("User", {
+      group = group,
+      pattern = "CodeDiffClose",
+      callback = function(ev)
+        diff_tabs[ev.data.tabpage] = nil
+        -- Fires before the tab is gone, so TabClosed does the actual unmuting
+        sync_animations()
+      end,
+    })
+
+    vim.api.nvim_create_autocmd({ "TabEnter", "TabClosed" }, {
+      group = group,
+      callback = sync_animations,
+    })
+  end,
 }