perf(git): run git log sync with bounded count

lua/git/log.lua

@@ -6,19 +6,26 @@ local util = require("util")
 local M = {}
 
 local LOG_FORMAT = "%h %ad {%an}%d %s"
+local DEFAULT_MAX_COUNT = 1000
+
+---@class ow.Git.LogOpts
+---@field max_count integer?  cap on commits to show. Nil uses the default, <= 0 means "all"
+
+---@param opts ow.Git.LogOpts?
+function M.show(opts)
+    opts = opts or {}
+    local max_count = opts.max_count
+    if max_count == nil then
+        max_count = DEFAULT_MAX_COUNT
+    end
 
-function M.show()
     local _, worktree = repo.resolve_cwd()
     if not worktree then
         log.warning("not in a git repository")
         return
     end
 
-    local buf = git.new_scratch()
-    vim.b[buf].git_worktree = worktree
-
-    vim.system(
-        {
+    local cmd = {
         "git",
         "log",
         "--graph",
@@ -26,24 +33,30 @@ function M.show()
         "--decorate",
         "--date=short",
         "--format=format:" .. LOG_FORMAT,
-        },
-        { cwd = worktree, text = true },
-        vim.schedule_wrap(function(result)
-            if not vim.api.nvim_buf_is_valid(buf) then
-                return
+    }
+    if max_count > 0 then
+        table.insert(cmd, "--max-count=" .. max_count)
     end
+
+    local result = vim.system(cmd, { cwd = worktree, text = true }):wait()
     if result.code ~= 0 then
         log.error("git log failed: %s", vim.trim(result.stderr or ""))
         return
     end
-            local lines = util.split_lines(result.stdout or "")
+
+    local buf = git.new_scratch()
+    vim.b[buf].git_worktree = worktree
     vim.bo[buf].modifiable = true
-            vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+    vim.api.nvim_buf_set_lines(
+        buf,
+        0,
+        -1,
+        false,
+        util.split_lines(result.stdout or "")
+    )
     vim.bo[buf].modifiable = false
     vim.bo[buf].modified = false
     vim.bo[buf].filetype = "gitlog"
-        end)
-    )
 end
 
 return M

lua/git/sidebar.lua

@@ -214,14 +214,13 @@ local function parse_porcelain(stdout)
     return branch, groups
 end
 
----Run the ahead/behind `git log` calls for any non-zero counters and call
----`callback(branch, groups)` once they all finish (or immediately when
----there's nothing to fetch).
+---Fill in the Unpushed/Unpulled groups from `git log` for any non-zero
+---ahead/behind counter. Capped at 200 commits per range so a wildly
+---divergent branch can't blow the sidebar's render budget.
 ---@param worktree string
 ---@param branch ow.Git.BranchInfo
 ---@param groups table<string, ow.Git.SidebarEntry[]>
----@param callback fun(branch: ow.Git.BranchInfo, groups: table<string, ow.Git.SidebarEntry[]>)
-local function enrich_with_log(worktree, branch, groups, callback)
+local function enrich_with_log(worktree, branch, groups)
     local fetches = {}
     if branch.upstream and branch.ahead > 0 then
         table.insert(
@@ -235,27 +234,29 @@ local function enrich_with_log(worktree, branch, groups, callback)
             { section = "Unpulled", range = "HEAD..@{upstream}" }
         )
     end
-    if #fetches == 0 then
-        callback(branch, groups)
-        return
-    end
-    local pending = #fetches
+    -- Submit both subprocesses before waiting so they run concurrently
+    -- rather than sequentially. Total time = max, not sum.
+    local pending = {}
     for _, f in ipairs(fetches) do
-        vim.system(
-            {
+        table.insert(pending, {
+            f = f,
+            sys = vim.system({
                 "git",
                 "log",
+                "--max-count=200",
                 "--format=%h %s",
                 f.range,
-            },
-            { cwd = worktree, text = true },
-            vim.schedule_wrap(function(log_obj)
-                if log_obj.code == 0 then
-                    for line in (log_obj.stdout or ""):gmatch("[^\r\n]+") do
+            }, { cwd = worktree, text = true }),
+        })
+    end
+    for _, p in ipairs(pending) do
+        local result = p.sys:wait()
+        if result.code == 0 then
+            for line in (result.stdout or ""):gmatch("[^\r\n]+") do
                 local sha, subject = line:match("^(%S+)%s+(.+)$")
                 if sha then
-                            table.insert(groups[f.section], {
-                                section = f.section,
+                    table.insert(groups[p.f.section], {
+                        section = p.f.section,
                         sha = sha,
                         subject = subject,
                     })
@@ -264,16 +265,10 @@ local function enrich_with_log(worktree, branch, groups, callback)
         else
             log.error(
                 "git log %s failed: %s",
-                        f.range,
-                        vim.trim(log_obj.stderr or "")
+                p.f.range,
+                vim.trim(result.stderr or "")
             )
         end
-                pending = pending - 1
-                if pending == 0 then
-                    callback(branch, groups)
-                end
-            end)
-        )
     end
 end
 
@@ -287,7 +282,8 @@ end
 local function fetch_status(worktree, prefetched_stdout, callback)
     if prefetched_stdout then
         local branch, groups = parse_porcelain(prefetched_stdout)
-        enrich_with_log(worktree, branch, groups, callback)
+        enrich_with_log(worktree, branch, groups)
+        callback(branch, groups)
         return
     end
     vim.system(
@@ -316,7 +312,8 @@ local function fetch_status(worktree, prefetched_stdout, callback)
                 return
             end
             local branch, groups = parse_porcelain(obj.stdout or "")
-            enrich_with_log(worktree, branch, groups, callback)
+            enrich_with_log(worktree, branch, groups)
+            callback(branch, groups)
         end)
     )
 end