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

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(
@@ -235,45 +234,41 @@ 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
-                        local sha, subject = line:match("^(%S+)%s+(.+)$")
-                        if sha then
-                            table.insert(groups[f.section], {
-                                section = f.section,
-                                sha = sha,
-                                subject = subject,
-                            })
-                        end
-                    end
-                else
-                    log.error(
-                        "git log %s failed: %s",
-                        f.range,
-                        vim.trim(log_obj.stderr or "")
-                    )
+            }, { cwd = worktree, text = true }),
+        })
+    end
+    for _, p in ipairs(pending) do
+        local result = p.sys:wait()
+        if result.code == 0 then
+            for line in (result.stdout or ""):gmatch("[^\r\n]+") do
+                local sha, subject = line:match("^(%S+)%s+(.+)$")
+                if sha then
+                    table.insert(groups[p.f.section], {
+                        section = p.f.section,
+                        sha = sha,
+                        subject = subject,
+                    })
                 end
-                pending = pending - 1
-                if pending == 0 then
-                    callback(branch, groups)
-                end
-            end)
-        )
+            end
+        else
+            log.error(
+                "git log %s failed: %s",
+                p.f.range,
+                vim.trim(result.stderr or "")
+            )
+        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