project: render worktree status from one snapshot

Use porcelain-v2 branch and path records to replace the status display
fan-out with one Git process on Git 2.11 and newer. Preserve the legacy
renderer for older clients, force rename and ahead/behind behavior where
supported, and fall back to the old divergence query only when status
cannot supply branch.ab.

Bug: 543851900
Bug: 553599402
Change-Id: Ic760360f4f48ab9320abf69dbbb7310dab4ac649
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/632144
Commit-Queue: Gavin Mak <gavinmak@google.com>
Reviewed-by: Brian Gan <brgan@google.com>
Tested-by: Gavin Mak <gavinmak@google.com>

git_status.py

@@ -91,8 +91,10 @@ def GetStatus(
     ]
     if branch:
         cmd.append("--branch")
-        if ahead_behind and git_require((2, 17, 0)):
-            cmd.append("--ahead-behind")
+        if git_require((2, 17, 0)):
+            cmd.append(
+                "--ahead-behind" if ahead_behind else "--no-ahead-behind"
+            )
     if git_require((2, 18, 0)):
         # Match the existing staged diff's explicit rename detection even if
         # status.renames is disabled in the user's config.