ignore: fix include: rules depending on current directory (issue4759)

When reading pattern files, we just call open(path), which is relative to the
current directory.  Let's fix this by resolving the paths before attempting to
read the file.

mercurial/match.py

@@ -289,7 +289,8 b' class match(object):'
                 continue
             elif kind == 'include':
                 try:
-                    includepats = readpatternfile(pat, self._warn)
+                    fullpath = pathutil.join(root, pat)
+                    includepats = readpatternfile(fullpath, self._warn)
                     for k, p, source in self._normalize(includepats, default,
                                                         root, cwd, auditor):
                         kindpats.append((k, p, source or pat))

tests/test-hgignore.t

@@ -186,8 +186,9 b" Check using 'include:' in ignore file"
 
 Check recursive uses of 'include:'
 
-  $ echo "include:nestedignore" >> otherignore
-  $ echo "glob:*ignore" > nestedignore
+  $ echo "include:nested/ignore" >> otherignore
+  $ mkdir nested
+  $ echo "glob:*ignore" > nested/ignore
   $ hg status
   A dir/b.o
 
@@ -199,6 +200,13 b" Check recursive uses of 'include:'"
 
   $ mv goodignore otherignore
 
+Check using 'include:' while in a non-root directory
+
+  $ cd ..
+  $ hg -R ignorerepo status
+  A dir/b.o
+  $ cd ignorerepo
+
 Check including subincludes
 
   $ hg revert -q --all