config: give it an includepaths option for looking for config files

It is desirable to "derive" templates from the provided templates. A
simple way to do this is e.g.

    %include map-cmdline.default

in your own mapfile. Then you only have to redefine a few templates
instead of copying over the whole thing. This %include mechanism
already works for the built-in templates because by default it *only*
looks for files that are in the same directory as the including
mapfile.

With this changeset, config grows an option to add more include paths
for config files.

mercurial/config.py

@@ -1,159 +1,164 b''
 # config.py - configuration parsing for Mercurial
 #
 #  Copyright 2009 Matt Mackall <[e-mail]> and others
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from i18n import _
 import error, util
 import os, errno
 
 class config(object):
-    def __init__(self, data=None):
+    def __init__(self, data=None, includepaths=[]):
         self._data = {}
         self._source = {}
         self._unset = []
+        self._includepaths = includepaths
         if data:
             for k in data._data:
                 self._data[k] = data[k].copy()
             self._source = data._source.copy()
     def copy(self):
         return config(self)
     def __contains__(self, section):
         return section in self._data
     def __getitem__(self, section):
         return self._data.get(section, {})
     def __iter__(self):
         for d in self.sections():
             yield d
     def update(self, src):
         for s, n in src._unset:
             if s in self and n in self._data[s]:
                 del self._data[s][n]
                 del self._source[(s, n)]
         for s in src:
             if s not in self:
                 self._data[s] = util.sortdict()
             self._data[s].update(src._data[s])
         self._source.update(src._source)
     def get(self, section, item, default=None):
         return self._data.get(section, {}).get(item, default)
 
     def backup(self, section, item):
         """return a tuple allowing restore to reinstall a previous value
 
         The main reason we need it is because it handles the "no data" case.
         """
         try:
             value = self._data[section][item]
             source = self.source(section, item)
             return (section, item, value, source)
         except KeyError:
             return (section, item)
 
     def source(self, section, item):
         return self._source.get((section, item), "")
     def sections(self):
         return sorted(self._data.keys())
     def items(self, section):
         return self._data.get(section, {}).items()
     def set(self, section, item, value, source=""):
         if section not in self:
             self._data[section] = util.sortdict()
         self._data[section][item] = value
         if source:
             self._source[(section, item)] = source
 
     def restore(self, data):
         """restore data returned by self.backup"""
         if len(data) == 4:
             # restore old data
             section, item, value, source = data
             self._data[section][item] = value
             self._source[(section, item)] = source
         else:
             # no data before, remove everything
             section, item = data
             if section in self._data:
                 self._data[section].pop(item, None)
             self._source.pop((section, item), None)
 
     def parse(self, src, data, sections=None, remap=None, include=None):
         sectionre = util.re.compile(r'\[([^\[]+)\]')
         itemre = util.re.compile(r'([^=\s][^=]*?)\s*=\s*(.*\S|)')
         contre = util.re.compile(r'\s+(\S|\S.*\S)\s*$')
         emptyre = util.re.compile(r'(;|#|\s*$)')
         commentre = util.re.compile(r'(;|#)')
         unsetre = util.re.compile(r'%unset\s+(\S+)')
         includere = util.re.compile(r'%include\s+(\S|\S.*\S)\s*$')
         section = ""
         item = None
         line = 0
         cont = False
 
         for l in data.splitlines(True):
             line += 1
             if line == 1 and l.startswith('\xef\xbb\xbf'):
                 # Someone set us up the BOM
                 l = l[3:]
             if cont:
                 if commentre.match(l):
                     continue
                 m = contre.match(l)
                 if m:
                     if sections and section not in sections:
                         continue
                     v = self.get(section, item) + "\n" + m.group(1)
                     self.set(section, item, v, "%s:%d" % (src, line))
                     continue
                 item = None
                 cont = False
             m = includere.match(l)
-            if m:
-                inc = util.expandpath(m.group(1))
-                base = os.path.dirname(src)
-                inc = os.path.normpath(os.path.join(base, inc))
-                if include:
+
+            if m and include:
+                expanded = util.expandpath(m.group(1))
+                includepaths = [os.path.dirname(src)] + self._includepaths
+
+                for base in includepaths:
+                    inc = os.path.normpath(os.path.join(base, expanded))
+
                     try:
                         include(inc, remap=remap, sections=sections)
+                        break
                     except IOError, inst:
                         if inst.errno != errno.ENOENT:
                             raise error.ParseError(_("cannot include %s (%s)")
                                                    % (inc, inst.strerror),
                                                    "%s:%s" % (src, line))
                 continue
             if emptyre.match(l):
                 continue
             m = sectionre.match(l)
             if m:
                 section = m.group(1)
                 if remap:
                     section = remap.get(section, section)
                 if section not in self:
                     self._data[section] = util.sortdict()
                 continue
             m = itemre.match(l)
             if m:
                 item = m.group(1)
                 cont = True
                 if sections and section not in sections:
                     continue
                 self.set(section, item, m.group(2), "%s:%d" % (src, line))
                 continue
             m = unsetre.match(l)
             if m:
                 name = m.group(1)
                 if sections and section not in sections:
                     continue
                 if self.get(section, name) is not None:
                     del self._data[section][name]
                 self._unset.append((section, name))
                 continue
 
             raise error.ParseError(l.rstrip(), ("%s:%s" % (src, line)))
 
     def read(self, path, fp=None, sections=None, remap=None):
         if not fp:
             fp = util.posixfile(path)
         self.parse(path, fp.read(), sections, remap, self.read)