[PATCH 1 of 2 v2] configitems: add alias support in config

[David Demelier]

# HG changeset patch
# User David Demelier <demelier.david at gmail.com>
# Date 1498646676 -7200
#      Wed Jun 28 12:44:36 2017 +0200
# Node ID 9a80ff1ee41ce0c87cf1f7f5219b6337f3c04941
# Parent  247bae545061374a683d8d9369a4869aa6ae4537
configitems: add alias support in config

Aliases define optional alternatives to existing options. For example the old
option ui.user was deprecated and replaced by ui.username. With this mechanism,
it's even possible to create an alias to an option in a different section.

Add ui.user as alias to ui.username as an example of this concept.

The old alternates principle in ui.config is removed as it was used only for
this option.

diff -r 247bae545061 -r 9a80ff1ee41c mercurial/configitems.py
--- a/mercurial/configitems.py	Tue Jun 27 23:50:22 2017 +0900
+++ b/mercurial/configitems.py	Wed Jun 28 12:44:36 2017 +0200
@@ -19,9 +19,10 @@
     :default: default value for this item,
     """
 
-    def __init__(self, section, name, default=None):
+    def __init__(self, section, name, alias=None, default=None):
         self.section = section
         self.name = name
+        self.alias = alias
         self.default = default
 
 coreitems = {}
@@ -48,3 +49,6 @@
 coreconfigitem('ui', 'quiet',
     default=False,
 )
+coreconfigitem('ui', 'username',
+    alias=[('ui', 'user')]
+)
diff -r 247bae545061 -r 9a80ff1ee41c mercurial/ui.py
--- a/mercurial/ui.py	Tue Jun 27 23:50:22 2017 +0900
+++ b/mercurial/ui.py	Wed Jun 28 12:44:36 2017 +0200
@@ -448,36 +448,37 @@
 
     def _config(self, section, name, default=_unset, untrusted=False):
         value = default
-        if isinstance(name, list):
-            alternates = name
-        else:
-            item = self._knownconfig.get(section, {}).get(name)
-            if default is _unset:
-                if item is None:
-                    value = default
-                else:
-                    value = item.default
-            elif item is not None:
-                msg = ("specifying a default value for a registered "
-                       "config item: '%s.%s' '%s'")
-                msg %= (section, name, default)
-                self.develwarn(msg, 2, 'warn-config-default')
+        item = self._knownconfig.get(section, {}).get(name)
+        alternates = [(section, name)]
+
+        if item is not None and item.alias is not None:
+            alternates = alternates + item.alias
 
-            alternates = [name]
+        if default is _unset:
+            if item is None:
+                value = default
+            else:
+                value = item.default
+        elif item is not None:
+            msg = ("specifying a default value for a registered "
+                   "config item: '%s.%s' '%s'")
+            msg %= (section, name, default)
+            self.develwarn(msg, 2, 'warn-config-default')
 
-        for n in alternates:
-            candidate = self._data(untrusted).get(section, n, None)
+        for s, n in alternates:
+            candidate = self._data(untrusted).get(s, n, None)
             if candidate is not None:
                 value = candidate
+                section = s
                 name = n
                 break
 
         if self.debugflag and not untrusted and self._reportuntrusted:
-            for n in alternates:
-                uvalue = self._ucfg.get(section, n)
+            for s, n in alternates:
+                uvalue = self._ucfg.get(s, n)
                 if uvalue is not None and uvalue != value:
                     self.debug("ignoring untrusted configuration option "
-                               "%s.%s = %s\n" % (section, n, uvalue))
+                               "%s.%s = %s\n" % (s, n, uvalue))
         return value
 
     def configsuboptions(self, section, name, default=_unset, untrusted=False):
@@ -742,7 +743,7 @@
         """
         user = encoding.environ.get("HGUSER")
         if user is None:
-            user = self.config("ui", ["username", "user"])
+            user = self.config("ui", "username")
             if user is not None:
                 user = os.path.expandvars(user)
         if user is None:
diff -r 247bae545061 -r 9a80ff1ee41c tests/test-config-alias.t
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test-config-alias.t	Wed Jun 28 12:44:36 2017 +0200
@@ -0,0 +1,14 @@
+verify that aliases are evaluated as well
+
+  $ hg init aliastest
+  $ cd aliastest
+  $ cat > .hg/hgrc << EOF
+  > [ui]
+  > user = repo user
+  > EOF
+  $ touch index
+  $ unset HGUSER
+  $ hg ci -Am test
+  adding index
+  $ hg log --template '{author}\n'
+  repo user