sync: Only parallelize gc for git >= 1.7.2

This minimum version is required for the -c argument to set config on
the command line. Without this option, git by default uses as many
threads per invocation as there are CPUs, so we cannot safely
parallelize without hosing a system.

Change-Id: I8fd313dd84917658162b5134b2d9aa34a96f2772

1 files changed, 3 insertions, 2 deletions

diff --git a/subcmds/sync.py b/subcmds/sync.py
index 8e9477a3..15f69f7b 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -44,7 +44,7 @@ try:
 except ImportError:
   multiprocessing = None
 
-from git_command import GIT
+from git_command import GIT, git_require
 from git_refs import R_HEADS, HEAD
 from main import WrapperModule
 from project import Project
@@ -310,7 +310,8 @@ later is required to fix a server side protocol bug.
     return fetched
 
   def _GCProjects(self, projects):
-    if multiprocessing:
+    has_dash_c = git_require((1, 7, 2))
+    if multiprocessing and has_dash_c:
       cpu_count = multiprocessing.cpu_count()
     else:
       cpu_count = 1