relnotes: document changed behavior of ui.origbackuppath pointing to file

Differential Revision: https://phab.mercurial-scm.org/D6446

relnotes/next

@@ -1,37 +1,42
 == New Features ==
 
  * New config `commands.commit.post-status` shows status after successful
  commit.
 
 
 == New Experimental Features ==
 
  * New config `experimental.log.topo` makes `hg log -G` use
    topological sorting. This is especially useful for aliases since it
    lets the alias accept an `-r` option while still using topological
    sorting with or without the `-r` (unlike if you use the `sort(...,
    topo)` revset).
 
 
 == Bug Fixes  ==
 
 
 == Backwards Compatibility Changes ==
 
  * Removed (experimental) support for log graph lines mixing
    parent/grandparent styles. Setting
    e.g. `experimental.graphstyle.parent = !` and
    `experimental.graphstyle.grandparent = 3.` would use `!` for the
    first three lines of the graph and then `.`. This is no longer
    supported.
 
+ * If `ui.origbackuppath` had been (incorrectly) configured to point
+   to a file, we will now replace that file by a directory and put
+   backups in that directory. This is similar to how we would
+   previously replace files *in* the configured directory by
+   subdirectories.
 
 == Internal API Changes ==
 
  * Matchers are no longer iterable. Use `match.files()` instead.
 
  * `match.visitdir()` and `match.visitchildrenset()` now expect the
    empty string instead of '.' to indicate the root directory.
 
  * `util.dirs()` and `util.finddirs()` now include an entry for the
    root directory (empty string).