Split out command-line formatting into a separate utility function.

diffoscope/comparators/utils/command.py

@@ -22,6 +22,8 @@ import logging
 import shlex
 import subprocess
 
+from ...utils import format_cmdline
+
 logger = logging.getLogger(__name__)
 
 
@@ -65,16 +67,9 @@ class Command(metaclass=abc.ABCMeta):
     def cmdline(self):
         raise NotImplementedError()
 
-    def shell_cmdline(self):
-        def fn(x):
-            if x == self.path:
-                return '{}'
-            x = repr(x)
-            if ' ' not in x:
-                x = x[1:-1]
-            return x
-
-        return ' '.join(fn(x) for x in self.cmdline())
+    def shell_cmdline(self, *args, **kwargs):
+        kwargs.setdefault('replace', (self.path,))
+        return format_cmdline(self.cmdline(), *args, **kwargs)
 
     def env(self):
         return None  # inherit parent environment by default

diffoscope/utils.py

+# -*- coding: utf-8 -*-
+#
+# diffoscope: in-depth comparison of files, archives, and directories
+#
+# Copyright © 2019 Chris Lamb <lamby@debian.org>
+#
+# diffoscope is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# diffoscope is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with diffoscope.  If not, see <https://www.gnu.org/licenses/>.
+
+
+def format_cmdline(cmd, replace=()):
+    def fn(x):
+        if x in replace:
+            return '{}'
+        x = repr(x)
+        if ' ' not in x:
+            x = x[1:-1]
+        return x
+
+    return ' '.join(fn(x) for x in cmd)