zero-bytes wc.db appeared in my format-9 wc (causes 'svn upgrade' => 'no such table wcroot')

[Daniel Shahaf]

I have a format-9 wc, which complains "svn: no such table: wcroot"
whenever I try to 'svn upgrade' it using current trunk:

    [ in a wc of trunk ]
    % ./subversion/svn/svn up
    At revision 965241.
    % make
    % svnversion ../atomic-revprop 
    965241
    % ./subversion/svn/svn upgrade ../atomic-revprop
    subversion/svn/upgrade-cmd.c:73: (apr_err=200030)
    subversion/libsvn_client/cleanup.c:131: (apr_err=200030)
    subversion/libsvn_wc/upgrade.c:1605: (apr_err=200030)
    subversion/libsvn_wc/upgrade.c:1529: (apr_err=200030)
    subversion/libsvn_wc/wc_db.c:6901: (apr_err=200030)
    subversion/libsvn_wc/wc_db_pdh.c:596: (apr_err=200030)
    subversion/libsvn_wc/wc_db_util.c:64: (apr_err=200030)
    subversion/libsvn_subr/sqlite.c:146: (apr_err=200030)
    subversion/libsvn_subr/sqlite.c:164: (apr_err=200030)
    svn: no such table: wcroot

Further, that wc seems to be confused as to its version:

    % cat ../atomic-revprop/.svn/format 
    9
    % ls -l ../atomic-revprop/.svn/wc.db 
    -rw-r--r-- 1 daniel daniel 0 2010-07-17 15:31 ../atomic-revprop/.svn/wc.db

And, indeed, removing the empty wc.db file allows the upgrade to go through.

I'm not sure what I did to cause the empty wc.db to appear :-(

Daniel
(I previously upgraded just the tests/cmdline/ directory, but subsequently
rm -rf'd it and then restored it by 'svn up' using the 1.5 client.)