Description of problem:
mock caches directories added to a jail using bind_mount_opts config options. This makes the cache extremely large and takes very long time if the mounted directory is large.


Version-Release number of selected component (if applicable): Discovered in mock-1.1.12-1.fc15.noarch. I believe that this is still the problem in 1.1.15.


How reproducible:
Every time


Steps to Reproduce:
1.Added the following to my /etc/mock/site-defaults.cfg
config_opts['plugin_conf']['bind_mount_opts']['dirs'].append(('/users', '/users' ))

/users contains several home directories so it is very large.

2.Executed mock -r rhel-5-i386 --buildsrpm --spec mbe.spec --sources SOURCES --no-cleanup-after --resultdir=results --unpriv  --uniqueext=mbe

  
Actual results:
It took a very long time for the command to complete. The cache file contained /users


Expected results:
The cache file should not contain /users. bind mounted directories should not be cached since they presumably can be mounted again.


Additional info:
Here is a little patch that I added in order to avoid this problem:

diff --git a/py/mockbuild/plugins/root_cache.py b/py/mockbuild/plugins/root_cache.py
index ac53a2f..898f96f 100644
--- a/py/mockbuild/plugins/root_cache.py
+++ b/py/mockbuild/plugins/root_cache.py
@@ -127,7 +127,7 @@ class RootCache(object):
                 self.state("creating cache")
                 try:
                     mockbuild.util.do(
-                        ["tar"] + self.compressArgs + ["-cf", self.rootCacheFile,
+                        ["tar"] + ["--one-file-system"] + self.compressArgs + ["-cf", self.rootCacheFile,
                                                        "-C", self.rootObj.makeChrootPath()] +
                         self.exclude_tar_cmds + ["."],
                         shell=False