[git-llvm] Use --force-interactive when commiting to prompt password

[mehdi_amini]

Summary

When svn does not know the password and it has to prompt, it needs to query.
However it won't when invoked from the Python script and instead fails with:

svn: E215004: Authentication failed and interactive prompting is disabled; see the --force-interactive option

llvm/utils/git-svn/git-llvm

def svn_push_one_rev(svn_repo, rev, dry_run):
     for l in (l for l in status_lines if l.startswith('?')):
         svn(svn_repo, 'add', l[1:].strip())
     for l in (l for l in status_lines if l.startswith('!')):
         svn(svn_repo, 'remove', l[1:].strip())
 
     # Now we're ready to commit.
     commit_msg = git('show', '--pretty=%B', '--quiet', rev)
     if not dry_run:
-        log(svn(svn_repo, 'commit', '-m', commit_msg))
+        log(svn(svn_repo, 'commit', '-m', commit_msg, '--force-interactive'))
         log('Committed %s to svn.' % rev)
     else:
         log("Would have committed %s to svn, if this weren't a dry run." % rev)
 
 
 def cmd_push(args):
     '''Push changes back to SVN: this is extracted from Justin Lebar's script
     available here: https://github.com/jlebar/llvm-repo-tools/