Don't open relative files in fuzzy_url with :open

With most actions which use fuzzy_url (:open/quickmarks/etc.) it's rather
confusing when relative files are opened - the only place where they should be
opened is when we're processing a commandline argument.

qutebrowser/app.py

@@ -330,7 +330,7 @@ class Application(QApplication):
                                             window=win_id)
                 log.init.debug("Startup URL {}".format(cmd))
                 try:
-                    url = urlutils.fuzzy_url(cmd, cwd)
+                    url = urlutils.fuzzy_url(cmd, cwd, relative=True)
                 except urlutils.FuzzyUrlError as e:
                     message.error(0, "Error in startup argument '{}': "
                                      "{}".format(cmd, e))

qutebrowser/utils/urlutils.py

@@ -123,23 +123,30 @@ def _is_url_dns(url):
     return not info.error()
 
 
-def fuzzy_url(urlstr, cwd=None):
+def fuzzy_url(urlstr, cwd=None, relative=False):
     """Get a QUrl based on an user input which is URL or search term.
 
     Args:
         urlstr: URL to load as a string.
         cwd: The current working directory, or None.
+        relative: Whether to resolve relative files.
 
     Return:
         A target QUrl to a searchpage or the original URL.
     """
-    if cwd:
-        path = os.path.join(cwd, os.path.expanduser(urlstr))
-    else:
+    expanded = os.path.expanduser(urlstr)
+    if relative and cwd:
+        path = os.path.join(cwd, expanded)
+    elif relative:
         try:
-            path = os.path.abspath(os.path.expanduser(urlstr))
+            path = os.path.abspath(expanded)
         except OSError:
             path = None
+    elif os.path.isabs(expanded):
+        path = expanded
+    else:
+        path = None
+
     stripped = urlstr.strip()
     if path is not None and os.path.exists(path):
         log.url.debug("URL is a local file")