diff mercurial/help.py @ 44341:142d2a4cb69a

help: add a mechanism to change flags' help depending on config

It seems reasonable to have a similar mechanism for the rest of the
help, but no such thing is implemented.

The goal is to make the help of commands clearer in the presence of
significant default changes, like tweakdefaults or with company-wide
hgrcs. In these cases, a user looking at the help of a command doesn't
exactly know what his hgrc is doing.

Apply to this to the --git option of commands that display diffs, as
this option in particular causes confusion for some reason.

Differential Revision: https://phab.mercurial-scm.org/D8100

--- a/mercurial/help.py	Sat Feb 08 23:39:55 2020 -0500
+++ b/mercurial/help.py	Sun Feb 09 15:50:36 2020 -0500
@@ -152,8 +152,17 @@
     doc = b''.join(rst)
     return doc
 
+def parsedefaultmarker(text):
+    """given a text 'abc (DEFAULT: def.ghi)',
+    returns (b'abc', (b'def', b'ghi')). Otherwise return None"""
+    if text[-1:] == b')':
+        marker = b' (DEFAULT: '
+        pos = text.find(marker)
+        if pos >= 0:
+            item = text[pos + len(marker):-1]
+            return text[:pos], item.split(b'.', 2)
 
-def optrst(header, options, verbose):
+def optrst(header, options, verbose, ui):
     data = []
     multioccur = False
     for option in options:
@@ -165,7 +174,14 @@
 
         if not verbose and any(w in desc for w in _exclkeywords):
             continue
-
+        defaultstrsuffix = b''
+        if default is None:
+            parseresult = parsedefaultmarker(desc)
+            if parseresult is not None:
+                (desc, (section, name)) = parseresult
+                if ui.configbool(section, name):
+                    default = True
+                    defaultstrsuffix = _(b' from config')
         so = b''
         if shortopt:
             so = b'-' + shortopt
@@ -183,7 +199,7 @@
             defaultstr = pycompat.bytestr(default)
             if default is True:
                 defaultstr = _(b"on")
-            desc += _(b" (default: %s)") % defaultstr
+            desc += _(b" (default: %s)") % (defaultstr + defaultstrsuffix)
 
         if isinstance(default, list):
             lo += b" %s [+]" % optlabel
@@ -714,11 +730,11 @@
 
         # options
         if not ui.quiet and entry[1]:
-            rst.append(optrst(_(b"options"), entry[1], ui.verbose))
+            rst.append(optrst(_(b"options"), entry[1], ui.verbose, ui))
 
         if ui.verbose:
             rst.append(
-                optrst(_(b"global options"), commands.globalopts, ui.verbose)
+                optrst(_(b"global options"), commands.globalopts, ui.verbose, ui)
             )
 
         if not ui.verbose:
@@ -858,7 +874,7 @@
         elif ui.verbose:
             rst.append(
                 b'\n%s\n'
-                % optrst(_(b"global options"), commands.globalopts, ui.verbose)
+                % optrst(_(b"global options"), commands.globalopts, ui.verbose, ui)
             )
             if name == b'shortlist':
                 rst.append(