# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@fb.com>
# Date 2014-12-15 21:27:46
# Node ID aed981c7bebf3b63fbe9f777523a590d39f64bba
# Parent  e20f36ad092ef367c92f1c3729896264fa2ba42c

vfs: add a 'reljoin' function for joining relative paths

The vfs.join method only works for absolute paths. We need something
that works for relative paths too when transforming filenames. Since
os.path.join may misbehave in tricky encoding situations, encapsulate
the new join method in our vfs abstraction. The default implementation
remains os.path.join, but this opens the door to other VFSes doing
something more intelligent based on their needs.

In the same go, we replace the usage of 'os.path.join' in transaction code.

diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -261,6 +261,13 @@ class abstractvfs(object):
     def islink(self, path=None):
         return os.path.islink(self.join(path))
 
+    def reljoin(self, *paths):
+        """join various elements of a path together (as os.path.join would do)
+
+        The vfs base is not injected so that path stay relative. This exists
+        to allow handling of strange encoding if needed."""
+        return os.path.join(*paths)
+
     def lexists(self, path=None):
         return os.path.lexists(self.join(path))
 
diff --git a/mercurial/transaction.py b/mercurial/transaction.py
--- a/mercurial/transaction.py
+++ b/mercurial/transaction.py
@@ -200,8 +200,8 @@ class transaction(object):
             return
         dirname, filename = os.path.split(file)
         backupfilename = "%s.backup.%s" % (self.journal, filename)
-        backupfile = os.path.join(dirname, backupfilename)
         vfs = self._vfsmap[location]
+        backupfile = vfs.reljoin(dirname, backupfilename)
         if vfs.exists(file):
             filepath = vfs.join(file)
             backuppath = vfs.join(backupfile)