neovim: Restore gitsigns mappings

The defaults were not active anymore after the upgrade to 22.05.

users/simon/modules/neovim/init.lua

@@ -129,7 +129,47 @@ hi NeogitNotificationInfo guifg=#268bd2
 hi NeogitNotificationWarning guifg=#cb4b16
 hi NeogitNotificationError guifg=#dc322f
 ]])
-require('gitsigns').setup()
+require('gitsigns').setup {
+    -- copied from upstream readme
+    on_attach = function(bufnr)
+        local gs = package.loaded.gitsigns
+
+        local function map(mode, l, r, opts)
+            opts = opts or {}
+            opts.buffer = bufnr
+            vim.keymap.set(mode, l, r, opts)
+        end
+
+        -- Navigation
+        map('n', ']c', function()
+            if vim.wo.diff then return ']c' end
+            vim.schedule(function() gs.next_hunk() end)
+            return '<Ignore>'
+        end, {expr=true})
+
+        map('n', '[c', function()
+            if vim.wo.diff then return '[c' end
+            vim.schedule(function() gs.prev_hunk() end)
+            return '<Ignore>'
+        end, {expr=true})
+
+        -- Actions
+        map({'n', 'v'}, '<leader>hs', ':Gitsigns stage_hunk<CR>')
+        map({'n', 'v'}, '<leader>hr', ':Gitsigns reset_hunk<CR>')
+        map('n', '<leader>hS', gs.stage_buffer)
+        map('n', '<leader>hu', gs.undo_stage_hunk)
+        map('n', '<leader>hR', gs.reset_buffer)
+        map('n', '<leader>hp', gs.preview_hunk)
+        map('n', '<leader>hb', function() gs.blame_line{full=true} end)
+        map('n', '<leader>tb', gs.toggle_current_line_blame)
+        map('n', '<leader>hd', gs.diffthis)
+        map('n', '<leader>hD', function() gs.diffthis('~') end)
+        map('n', '<leader>td', gs.toggle_deleted)
+
+        -- Text object
+        map({'o', 'x'}, 'ih', ':<C-U>Gitsigns select_hunk<CR>')
+    end
+}
 require('diffview').setup {}
 
 -- Fuzzy finder/option picker