hgwebdir: allow a repository to be hosted at "/"

This can be useful in general, but will also be useful for hosting subrepos,
with the main repo at /.

mercurial/hgweb/hgweb_mod.py

@@ -335,7 +335,7 b' class hgweb(object):'
         req.url = req.env['SCRIPT_NAME']
         if not req.url.endswith('/'):
             req.url += '/'
-        if 'REPO_NAME' in req.env:
+        if req.env.get('REPO_NAME'):
             req.url += req.env['REPO_NAME'] + '/'
 
         if 'PATH_INFO' in req.env:

mercurial/hgweb/hgwebdir_mod.py

@@ -257,7 +257,7 b' class hgwebdir(object):'
 
             repos = dict(self.repos)
 
-            if not virtual or (virtual == 'index' and virtual not in repos):
+            if (not virtual or virtual == 'index') and virtual not in repos:
                 req.respond(HTTP_OK, ctype)
                 return self.makeindex(req, tmpl)
 
@@ -269,8 +269,17 b' class hgwebdir(object):'
                     req.respond(HTTP_OK, ctype)
                     return self.makeindex(req, tmpl, subdir)
 
-            virtualrepo = virtual
-            while virtualrepo:
+            def _virtualdirs():
+                # Check the full virtual path, each parent, and the root ('')
+                if virtual != '':
+                    yield virtual
+
+                    for p in util.finddirs(virtual):
+                        yield p
+
+                yield ''
+
+            for virtualrepo in _virtualdirs():
                 real = repos.get(virtualrepo)
                 if real:
                     req.env['REPO_NAME'] = virtualrepo
@@ -284,11 +293,6 b' class hgwebdir(object):'
                     except error.RepoError as inst:
                         raise ErrorResponse(HTTP_SERVER_ERROR, str(inst))
 
-                up = virtualrepo.rfind('/')
-                if up < 0:
-                    break
-                virtualrepo = virtualrepo[:up]
-
             # browse subdirectories
             subdir = virtual + '/'
             if [r for r in repos if r.startswith(subdir)]:

tests/test-hgwebdir.t

@@ -1680,6 +1680,22 b" Repos named 'index' take precedence over"
 
   $ killdaemons.py
 
+  $ cat > paths.conf << EOF
+  > [paths]
+  > / = $root/a
+  > EOF
+  $ hg serve -p $HGPORT1 -d --pid-file hg.pid --webdir-conf paths.conf
+  $ cat hg.pid >> $DAEMON_PIDS
+
+  $ hg id http://localhost:$HGPORT1
+  71a89161f014
+
+  $ get-with-headers.py localhost:$HGPORT1 '' | grep 'index'
+  <meta name="robots" content="index, nofollow" />
+     <a href="/rev/71a89161f014">add index file</a>
+
+  $ killdaemons.py
+
 paths errors 1
 
   $ cat error-paths-1.log