feat(git): trim hunk preview header, focus float on re-invoke

test/git/hunks_test.lua

@@ -52,6 +52,15 @@ local function detailed_marks(buf, ns_name)
     return vim.api.nvim_buf_get_extmarks(buf, ns, 0, -1, { details = true })
 end
 
+---@return integer?
+local function find_float()
+    for _, w in ipairs(vim.api.nvim_tabpage_list_wins(0)) do
+        if vim.api.nvim_win_get_config(w).relative ~= "" then
+            return w
+        end
+    end
+end
+
 t.test("pure add: hunk shape and add signs", function()
     local _, buf, state = setup("a\nd\n", "a\nb\nc\nd\n")
     t.eq(#state.hunks, 1, "one hunk for a pure addition")
@@ -296,6 +305,52 @@ t.test("git_hunk_signs falls back to the default for unset kinds", function()
     })
 end)
 
+t.test("preview_hunk shows the hunk body without file headers", function()
+    local _, buf = setup("a\nb\nc\n", "a\nB\nc\n")
+    vim.api.nvim_set_current_buf(buf)
+    vim.api.nvim_win_set_cursor(0, { 2, 0 })
+    hunks.preview_hunk(buf)
+    local float = assert(find_float(), "preview float should open")
+    t.defer(function()
+        pcall(vim.api.nvim_win_close, float, true)
+    end)
+    local lines = vim.api.nvim_buf_get_lines(
+        vim.api.nvim_win_get_buf(float),
+        0,
+        -1,
+        false
+    )
+    t.truthy(
+        vim.startswith(lines[1] or "", "@@ "),
+        "first line is the @@ header"
+    )
+    for _, l in ipairs(lines) do
+        t.falsy(vim.startswith(l, "--- "), "no --- file header line")
+        t.falsy(vim.startswith(l, "+++ "), "no +++ file header line")
+    end
+end)
+
+t.test("preview_hunk re-invocation focuses the open float", function()
+    local _, buf = setup("a\nb\nc\n", "a\nB\nc\n")
+    vim.api.nvim_set_current_buf(buf)
+    vim.api.nvim_win_set_cursor(0, { 2, 0 })
+    hunks.preview_hunk(buf)
+    local float = assert(find_float(), "preview float should open")
+    t.defer(function()
+        pcall(vim.api.nvim_win_close, float, true)
+    end)
+    t.truthy(
+        vim.api.nvim_get_current_win() ~= float,
+        "the float opens unfocused"
+    )
+    hunks.preview_hunk(buf)
+    t.eq(
+        vim.api.nvim_get_current_win(),
+        float,
+        "re-invoking focuses the existing float"
+    )
+end)
+
 t.test("nav jumps to next and previous hunks with wrap", function()
     local _, buf = setup("a\nb\nc\nd\ne\n", "A\nb\nc\nd\nE\n")
     vim.api.nvim_set_current_buf(buf)