fix incorrect warning when walking on a particular rev
when a directory was given instead of a file it reported
incorrectly 'No such file or directory in rev <rev>'
we test if the file is a prefix directory
<div>
<a class="title" href="?cmd=changeset;node=#node#;style=gitweb"><span class="age">#date|age# ago</span>#desc|strip|firstline|escape#</a>
</div>
<div class="title_text">
<div class="log_link">
<a href="?cmd=changeset;node=#node#;style=gitweb">changeset</a><br/>
</div>
<i>#author|obfuscate# [#date|rfc822date#] rev #rev#</i><br/>
</div>
<div class="log_body">
#desc|strip|escape|addbreaks#
<br/>
<br/>
</div>