paths: add an argument to format the suboption display

We will use it in the next function to the delta policy display. It could also
be use to deal with the other special case in the command code, but that is
unnecessary churn for stable so that part will go on default.

mercurial/commands.py

@@ -5219,7 +5219,9 b' def paths(ui, repo, search=None, **opts)'
                     value = b'yes'
                 else:
                     value = b'no'
-            fm.condwrite(showsubopts, subopt, b'%s\n', pycompat.bytestr(value))
+            display = urlutil.path_suboptions_display[subopt]
+            value = display(value)
+            fm.condwrite(showsubopts, subopt, b'%s\n', value)
 
     fm.end()
 

mercurial/utils/urlutil.py

@@ -658,9 +658,11 b' class paths(dict):'
 
 
 _pathsuboptions = {}
+# a dictionnary of methods that can be used to format a sub-option value
+path_suboptions_display = {}
 
 
-def pathsuboption(option, attr):
+def pathsuboption(option, attr, display=pycompat.bytestr):
     """Decorator used to declare a path sub-option.
 
     Arguments are the sub-option name and the attribute it should set on
@@ -671,12 +673,16 b' def pathsuboption(option, attr):'
     The function should return the value that will be set on the ``path``
     instance.
 
+    The optional `display` argument is a function that can be used to format
+    the value when displayed to the user (like in `hg paths` for example).
+
     This decorator can be used to perform additional verification of
     sub-options and to change the type of sub-options.
     """
 
     def register(func):
         _pathsuboptions[option] = (attr, func)
+        path_suboptions_display[option] = display
         return func
 
     return register