sync: only use --cruft when git supports it.

git gc --cruft was added in 2.37.0.

Bug: https://crbug.com/gerrit/16270
Change-Id: I71e46741e33472a92f16d6f11c51a23e1e55d869
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/346577


Reviewed-by: Emily Shaffer <emilyshaffer@google.com>
Tested-by: LaMont Jones <lamontjones@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

subcmds/sync.py

@@ -800,7 +800,11 @@ later is required to fix a server side protocol bug.
 
     jobs = opt.jobs
 
-    gc_args = ('--auto', '--cruft')
+    gc_args = ['--auto']
+    backup_cruft = False
+    if git_require((2, 37, 0)):
+      gc_args.append('--cruft')
+      backup_cruft = True
     pack_refs_args = ()
     if jobs < 2:
       for (run_gc, bare_git) in tidy_dirs.values():
@@ -810,6 +814,7 @@ later is required to fix a server side protocol bug.
           bare_git.gc(*gc_args)
         else:
           bare_git.pack_refs(*pack_refs_args)
+        if backup_cruft:
           self._backup_cruft(bare_git)
       pm.end()
       return
@@ -834,6 +839,7 @@ later is required to fix a server side protocol bug.
           err_event.set()
           raise
       finally:
+        if backup_cruft:
           self._backup_cruft(bare_git)
         pm.finish(bare_git._project.name)
         sem.release()