fix: add WinResized handler to update blame window extmarks

When the blame window is resized, update the right-side extmarks
(heatmap indicators) to stay aligned with the window's right edge.

Co-authored-by: lewis6991 <lewis6991@gmail.com>

Author: Copilot

lua/gitsigns/actions/blame.lua

@@ -59,6 +59,25 @@ local function get_hash_color(sha)
   return hl_name
 end
 
+--- Create a right-side extmark for the blame heatmap
+--- @param bufnr integer
+--- @param lnum integer (1-indexed)
+--- @param win_width integer
+--- @param min_time integer
+--- @param max_time integer
+--- @param author_time integer
+local function set_right_extmark(bufnr, lnum, win_width, min_time, max_time, author_time)
+  api.nvim_buf_set_extmark(bufnr, ns, lnum - 1, 0, {
+    virt_text_win_col = win_width,
+    virt_text = {
+      {
+        '┃',
+        get_temp_hl(min_time, max_time, author_time, 0.5, true),
+      },
+    },
+  })
+end
+
 ---@param amount integer
 ---@param text string
 ---@return string
@@ -137,15 +156,7 @@ local function render(blame, win, main_win, buf_sha)
       hl_group = hash_hl,
     })
 
-    api.nvim_buf_set_extmark(bufnr, ns, i - 1, 0, {
-      virt_text_win_col = win_width,
-      virt_text = {
-        {
-          '┃',
-          get_temp_hl(min_time, max_time, blame_info.commit.author_time, 0.5, true),
-        },
-      },
-    })
+    set_right_extmark(bufnr, i, win_width, min_time, max_time, blame_info.commit.author_time)
 
     if not commit_lines[i] then
       api.nvim_buf_set_extmark(bufnr, ns, i - 1, 2, {
@@ -314,6 +325,38 @@ local function diff(bufnr, blm_win, blame)
   end
 end
 
+--- Update the right-side extmarks when the window is resized
+--- @param blm_bufnr integer
+--- @param blm_win integer
+--- @param entries table<integer,Gitsigns.BlameInfo?>
+--- @param min_time integer
+--- @param max_time integer
+local function update_right_extmarks(blm_bufnr, blm_win, entries, min_time, max_time)
+  if not api.nvim_win_is_valid(blm_win) or not api.nvim_buf_is_valid(blm_bufnr) then
+    return
+  end
+
+  -- Get the actual window width (not the content width)
+  -- Subtract 1 because virt_text_win_col is 0-indexed
+  local win_width = api.nvim_win_get_width(blm_win) - 1
+
+  -- Get all extmarks and delete only those with virt_text_win_col
+  -- These are the right-side heatmap indicators that need repositioning
+  local extmarks = api.nvim_buf_get_extmarks(blm_bufnr, ns, 0, -1, { details = true })
+
+  for _, ext in ipairs(extmarks) do
+    local id, row, col, details = ext[1], ext[2], ext[3], ext[4]
+    if details.virt_text_win_col then
+      api.nvim_buf_del_extmark(blm_bufnr, ns, id)
+    end
+  end
+
+  -- Recreate the right-side extmarks with updated position
+  for i, blame_info in ipairs(entries) do
+    set_right_extmark(blm_bufnr, i, win_width, min_time, max_time, blame_info.commit.author_time)
+  end
+end
+
 --- @param mode string
 --- @param lhs string
 --- @param cb fun()
@@ -481,6 +524,16 @@ function M.blame(opts)
     end,
   })
 
+  -- Update right-side extmarks on window resize
+  api.nvim_create_autocmd('WinResized', {
+    buffer = blm_bufnr,
+    group = group,
+    callback = function()
+      local min_time, max_time = assert(cache[bufnr]):get_blame_times()
+      update_right_extmarks(blm_bufnr, blm_win, blame.entries, min_time, max_time)
+    end,
+  })
+
   api.nvim_create_autocmd('WinClosed', {
     pattern = tostring(blm_win),
     group = group,