windows: use abspath in convert.git

We replace `os.path.abspath` with `util.abspath`. This should solve more "drive
capitalization" issue on Windows.

Differential Revision: https://phab.mercurial-scm.org/D11070

hgext/convert/git.py

@@ -14,6 +14,7 b' from mercurial import ('
     config,
     error,
     pycompat,
+    util,
 )
 
 from . import common
@@ -74,7 +75,7 b' class convert_git(common.converter_sourc'
 
         # Pass an absolute path to git to prevent from ever being interpreted
         # as a URL
-        path = os.path.abspath(path)
+        path = util.abspath(path)
 
         if os.path.isdir(path + b"/.git"):
             path += b"/.git"