Properly replace variables in set-cmd-text command

This fixes #123 and allows variables like {url:pretty} to be used with
set-cmd-text

qutebrowser/mainwindow/statusbar/command.py

@@ -23,7 +23,7 @@ from PyQt5.QtCore import pyqtSignal, pyqtSlot, Qt, QUrl, QSize
 from PyQt5.QtWidgets import QSizePolicy
 
 from qutebrowser.keyinput import modeman, modeparsers
-from qutebrowser.commands import cmdexc, cmdutils
+from qutebrowser.commands import cmdexc, cmdutils, runners
 from qutebrowser.misc import cmdhistory
 from qutebrowser.misc import miscwidgets as misc
 from qutebrowser.utils import usertypes, log, objreg, qtutils
@@ -105,24 +105,9 @@ class Command(misc.MinimalLineEditMixin, misc.CommandLineEdit):
             space: If given, a space is added to the end.
             append: If given, the text is appended to the current text.
         """
-        tabbed_browser = objreg.get('tabbed-browser', scope='window',
-                                    window=self._win_id)
-        if '{url}' in text:
-            try:
-                url = tabbed_browser.current_url().toString(
-                    QUrl.FullyEncoded | QUrl.RemovePassword)
-            except qtutils.QtValueError as e:
-                msg = "Current URL is invalid"
-                if e.reason:
-                    msg += " ({})".format(e.reason)
-                msg += "!"
-                raise cmdexc.CommandError(msg)
-            # FIXME we currently replace the URL in any place in the arguments,
-            # rather than just replacing it if it is a dedicated argument. We
-            # could split the args, but then trailing spaces would be lost, so
-            # I'm not sure what's the best thing to do here
-            # https://github.com/The-Compiler/qutebrowser/issues/123
-            text = text.replace('{url}', url)
+        args = text.split()
+        args = runners.replace_variables(self._win_id, args)
+        text = ' '.join(args)
 
         if space:
             text += ' '

tests/integration/features/misc.feature

@@ -15,9 +15,9 @@ Feature: Various utility commands.
 
     Scenario: :set-cmd-text with URL replacement
         When I open data/hello.txt
-        When I run :set-cmd-text :message-info >{url}<
+        When I run :set-cmd-text :message-info {url}
         And I run :command-accept
-        Then the message ">http://localhost:*/hello.txt<" should be shown
+        Then the message "http://localhost:*/hello.txt" should be shown
 
     Scenario: :set-cmd-text with -s and -a
         When I run :set-cmd-text -s :message-info "foo