fix(history): include merge commits in file history and diff against …

lua/codediff/commands.lua

@@ -221,9 +221,7 @@ local function handle_history(range, file_path, flags, line_range, global_opts)
 
   local function open_history(git_root)
     -- Build options for commit list
-    local history_opts = {
-      no_merges = true,
-    }
+    local history_opts = {}
 
     -- Apply reverse flag if present
     if flags.reverse then
@@ -275,6 +273,7 @@ local function handle_history(range, file_path, flags, line_range, global_opts)
             range = range,
             file_path = history_opts.path,
             base_revision = flags.base,
+            reverse = history_opts.reverse,
             line_range = line_range,
           },
         }

lua/codediff/core/git.lua

@@ -782,18 +782,25 @@ function M.get_commit_list(range, git_root, opts, callback)
 
   local args = {
     "log",
-    "--pretty=format:%H%x00%h%x00%an%x00%at%x00%ar%x00%s%x00%D%x00",
+    "--pretty=format:%H%x00%h%x00%an%x00%at%x00%ar%x00%s%x00%D%x00%P",
   }
 
   if is_line_range then
     -- git log -L requires -p or -s format; --numstat/--shortstat/--follow are incompatible
     local l_arg = string.format("-L%d,%d:%s", opts.line_range[1], opts.line_range[2], opts.path)
     table.insert(args, l_arg)
   elseif is_single_file then
+    -- For single file mode, keep full history and request first-parent merge diffs
+    -- so merge commits that touched the file remain visible without duplicating
+    -- one entry per parent.
+    table.insert(args, "--full-history")
+    table.insert(args, "--diff-merges=first-parent")
     -- For single file mode, use --numstat to get stats AND file path (for renames)
     table.insert(args, "--numstat")
     table.insert(args, "--follow")
   else
+    -- For commit history mode, show merge commit stats against first parent.
+    table.insert(args, "--diff-merges=first-parent")
     -- For multi-file mode, use --shortstat for aggregate stats
     table.insert(args, "--shortstat")
   end
@@ -839,7 +846,8 @@ function M.get_commit_list(range, git_root, opts, callback)
         end
 
         local parts = vim.split(line, "\0")
-        if #parts >= 7 then
+        if #parts >= 8 then
+          local parent_hashes = parts[8] ~= "" and vim.split(parts[8], " ", { trimempty = true }) or {}
           current_commit = {
             hash = parts[1],
             short_hash = parts[2],
@@ -848,6 +856,9 @@ function M.get_commit_list(range, git_root, opts, callback)
             date_relative = parts[5],
             subject = parts[6],
             ref_names = parts[7] ~= "" and parts[7] or nil,
+            parent_hashes = parent_hashes,
+            parent_count = #parent_hashes,
+            parent_revision = parent_hashes[1],
             files_changed = 0,
             insertions = 0,
             deletions = 0,
@@ -914,8 +925,36 @@ end
 -- git_root: absolute path to git repository root
 -- callback: function(err, files) where files is array of:
 --   { path, status, old_path }
-function M.get_commit_files(commit_hash, git_root, callback)
-  run_git_async({ "diff-tree", "--no-commit-id", "--name-status", "-r", "-M", commit_hash }, { cwd = git_root }, function(err, output)
+function M.get_commit_files(commit_hash, git_root, opts, callback)
+  if type(opts) == "function" then
+    callback = opts
+    opts = {}
+  end
+
+  opts = opts or {}
+
+  local args
+  if opts.parent_revision and opts.parent_revision ~= "" then
+    args = {
+      "diff",
+      "--name-status",
+      "-M",
+      opts.parent_revision,
+      commit_hash,
+    }
+  else
+    args = {
+      "diff-tree",
+      "--root",
+      "--no-commit-id",
+      "--name-status",
+      "-r",
+      "-M",
+      commit_hash,
+    }
+  end
+
+  run_git_async(args, { cwd = git_root }, function(err, output)
     if err then
       callback(err, nil)
       return

lua/codediff/ui/history/nodes.lua

@@ -75,8 +75,11 @@ end
 -- files: array of { path, status, old_path }
 -- commit_hash: the commit hash these files belong to
 -- git_root: absolute path to git repository root
-function M.create_list_file_nodes(files, commit_hash, git_root)
+function M.create_list_file_nodes(files, commit_data, git_root)
   local file_nodes = {}
+  local commit_hash = commit_data.hash
+  local parent_revision = commit_data.parent_revision
+  local parent_count = commit_data.parent_count
 
   for i, file in ipairs(files) do
     local icon, icon_color = M.get_file_icon(file.path)
@@ -96,6 +99,8 @@ function M.create_list_file_nodes(files, commit_hash, git_root)
         status_color = status_info.color,
         git_root = git_root,
         commit_hash = commit_hash,
+        parent_revision = parent_revision,
+        parent_count = parent_count,
         is_last = i == #files,
         indent_state = { i == #files },
       },
@@ -109,9 +114,12 @@ end
 -- files: array of { path, status, old_path }
 -- commit_hash: the commit hash these files belong to
 -- git_root: absolute path to git repository root
-function M.create_tree_file_nodes(files, commit_hash, git_root)
+function M.create_tree_file_nodes(files, commit_data, git_root)
   -- Build directory structure
   local dir_tree = {}
+  local commit_hash = commit_data.hash
+  local parent_revision = commit_data.parent_revision
+  local parent_count = commit_data.parent_count
 
   for _, file in ipairs(files) do
     local parts = {}
@@ -202,6 +210,8 @@ function M.create_tree_file_nodes(files, commit_hash, git_root)
             status_color = status_info.color,
             git_root = git_root,
             commit_hash = commit_hash,
+            parent_revision = parent_revision,
+            parent_count = parent_count,
             indent_state = node_indent_state,
           },
         })

lua/codediff/ui/history/refresh.lua

@@ -125,9 +125,14 @@ function M.refresh(history)
 
   -- Reconstruct git log options
   local git_opts = {
-    no_merges = true,
     path = history.opts.file_path,
   }
+  if history.opts.reverse then
+    git_opts.reverse = true
+  end
+  if history.opts.line_range then
+    git_opts.line_range = history.opts.line_range
+  end
   if not history.opts.range or history.opts.range == "" then
     git_opts.limit = 100
   end

lua/codediff/ui/history/render.lua

@@ -71,6 +71,9 @@ function M.build_tree_nodes(commits, git_root, opts)
         date_relative = commit.date_relative,
         subject = commit.subject,
         ref_names = commit.ref_names,
+        parent_hashes = commit.parent_hashes,
+        parent_count = commit.parent_count,
+        parent_revision = commit.parent_revision,
         files_changed = commit.files_changed,
         insertions = commit.insertions,
         deletions = commit.deletions,
@@ -205,7 +208,7 @@ function M.create(commits, git_root, tabpage, width, opts)
       return
     end
 
-    git.get_commit_files(data.hash, git_root, function(err, files)
+    git.get_commit_files(data.hash, git_root, { parent_revision = data.parent_revision }, function(err, files)
       if err then
         vim.schedule(function()
           vim.notify("Failed to load commit files: " .. err, vim.log.levels.ERROR)
@@ -227,9 +230,9 @@ function M.create(commits, git_root, tabpage, width, opts)
 
         local file_nodes
         if view_mode == "tree" then
-          file_nodes = nodes_module.create_tree_file_nodes(files, data.hash, git_root)
+          file_nodes = nodes_module.create_tree_file_nodes(files, data, git_root)
         else
-          file_nodes = nodes_module.create_list_file_nodes(files, data.hash, git_root)
+          file_nodes = nodes_module.create_list_file_nodes(files, data, git_root)
         end
 
         -- Update node with children
@@ -275,6 +278,7 @@ function M.create(commits, git_root, tabpage, width, opts)
     local file_path = file_data.path
     local old_path = file_data.old_path
     local commit_hash = file_data.commit_hash
+    local parent_revision = file_data.parent_revision
 
     if not file_path or file_path == "" then
       vim.notify("[CodeDiff] No file path for selection", vim.log.levels.WARN)
@@ -287,7 +291,7 @@ function M.create(commits, git_root, tabpage, width, opts)
     end
 
     -- Check if already displaying same file
-    local target_hash = base_revision or (commit_hash .. "^")
+    local target_hash = base_revision or parent_revision or (commit_hash .. "^")
     local session = lifecycle.get_session(tabpage)
     if not opts.force and session and session.original_revision == target_hash and session.modified_revision == commit_hash then
       if session.modified_path == file_path or session.original_path == file_path then
@@ -369,6 +373,7 @@ function M.create(commits, git_root, tabpage, width, opts)
         local file_data = {
           path = file_path,
           commit_hash = first_commit_node.data.hash,
+          parent_revision = first_commit_node.data.parent_revision,
           git_root = git_root,
         }
         history.on_file_select(file_data)

tests/core/history_merge_spec.lua

@@ -0,0 +1,111 @@
+local git = require("codediff.core.git")
+local helpers = require("tests.helpers")
+
+describe("History merge commit support", function()
+  local repo = nil
+
+  before_each(function()
+    repo = helpers.create_temp_git_repo()
+
+    repo.write_file("target.txt", { "base" })
+    repo.git("add target.txt")
+    repo.git("commit -m 'base commit'")
+
+    repo.git("checkout -b feature")
+    repo.write_file("target.txt", { "feature change" })
+    repo.git("add target.txt")
+    repo.git("commit -m 'feature change'")
+
+    repo.git("checkout main")
+    repo.write_file("main.txt", { "main branch change" })
+    repo.git("add main.txt")
+    repo.git("commit -m 'main change'")
+
+    repo.git("merge --no-ff feature -m 'merge feature'")
+  end)
+
+  after_each(function()
+    if repo then
+      repo.cleanup()
+      repo = nil
+    end
+  end)
+
+  it("includes merge commits in single-file history", function()
+    local done = false
+    local err_result = nil
+    local commits_result = nil
+
+    git.get_commit_list("", repo.dir, { path = "target.txt" }, function(err, commits)
+      err_result = err
+      commits_result = commits
+      done = true
+    end)
+
+    helpers.wait_async(5000, function()
+      return done
+    end)
+
+    assert.is_nil(err_result)
+    assert.is_table(commits_result)
+    assert.is_true(#commits_result >= 2)
+
+    local merge_commit = nil
+    for _, commit in ipairs(commits_result) do
+      if commit.subject == "merge feature" then
+        merge_commit = commit
+        break
+      end
+    end
+
+    assert.is_not_nil(merge_commit, "Expected file history to include merge commit")
+    assert.equal(2, merge_commit.parent_count)
+    assert.is_not_nil(merge_commit.parent_revision)
+    assert.equal("target.txt", merge_commit.file_path)
+  end)
+
+  it("lists merge commit files against first parent", function()
+    local head_output = repo.git("rev-parse HEAD")
+    local merge_hash = vim.trim(head_output)
+
+    local list_done = false
+    local commits_result = nil
+    git.get_commit_list("", repo.dir, { path = "target.txt" }, function(_, commits)
+      commits_result = commits
+      list_done = true
+    end)
+
+    helpers.wait_async(5000, function()
+      return list_done
+    end)
+
+    local merge_commit = nil
+    for _, commit in ipairs(commits_result or {}) do
+      if commit.hash == merge_hash then
+        merge_commit = commit
+        break
+      end
+    end
+
+    assert.is_not_nil(merge_commit, "Expected HEAD merge commit in history list")
+
+    local done = false
+    local err_result = nil
+    local files_result = nil
+    git.get_commit_files(merge_commit.hash, repo.dir, { parent_revision = merge_commit.parent_revision }, function(err, files)
+      err_result = err
+      files_result = files
+      done = true
+    end)
+
+    helpers.wait_async(5000, function()
+      return done
+    end)
+
+    assert.is_nil(err_result)
+    assert.is_table(files_result)
+    assert.is_true(#files_result >= 1)
+    assert.equal("target.txt", files_result[1].path)
+    assert.equal("M", files_result[1].status)
+  end)
+end)