scmutil: fix requires-file isalnum() check on first byte
Slice instead of subscript to get a bytes from a bytes.
# skip-blame just a py3 slice-instead-of-subscript change
Differential Revision: https://phab.mercurial-scm.org/D2341
{header}
<title>{repo|escape}: {file|escape} annotate</title>
</head>
<body>
<div class="buttons">
<a href="{url|urlescape}log/{symrev}{sessionvars%urlparameter}">changelog</a>
<a href="{url|urlescape}shortlog/{symrev}{sessionvars%urlparameter}">shortlog</a>
<a href="{url|urlescape}graph/{symrev}{sessionvars%urlparameter}">graph</a>
<a href="{url|urlescape}tags{sessionvars%urlparameter}">tags</a>
<a href="{url|urlescape}branches{sessionvars%urlparameter}">branches</a>
<a href="{url|urlescape}rev/{symrev}{sessionvars%urlparameter}">changeset</a>
<a href="{url|urlescape}file/{symrev}{path|urlescape}{sessionvars%urlparameter}">files</a>
<a href="{url|urlescape}file/{symrev}/{file|urlescape}{sessionvars%urlparameter}">file</a>
<a href="{url|urlescape}log/{symrev}/{file|urlescape}{sessionvars%urlparameter}">revisions</a>
<a href="{url|urlescape}raw-file/{symrev}/{file|urlescape}">raw</a>
<a href="{url|urlescape}help{sessionvars%urlparameter}">help</a>
</div>
<h2><a href="/">Mercurial</a> {pathdef%breadcrumb} / annotate {file|escape}</h2>
<table>
<tr>
<td class="metatag">changeset {rev}:</td>
<td><a href="{url|urlescape}rev/{node|short}{sessionvars%urlparameter}">{node|short}</a></td>
</tr>
{parent%fileannotateparent}
{child%fileannotatechild}
<tr>
<td class="metatag">author:</td>
<td>{author|obfuscate}</td>
</tr>
<tr>
<td class="metatag">date:</td>
<td class="date age">{date|rfc822date}</td>
</tr>
<tr>
<td class="metatag">permissions:</td>
<td>{permissions|permissions}</td>
</tr>
<tr>
<td class="metatag">description:</td>
<td>{desc|strip|escape|websub|addbreaks|nonempty}</td>
</tr>
</table>
<table cellspacing="0" cellpadding="0">
{annotate%annotateline}
</table>
{footer}