merge: move forgets to the beginning of the action list

Forgets need to be in the beginning of the action list, same as removes. This
lets us avoid clashes in the dirstate where a directory is forgotten and a
file with the same name is added, or vice versa.

mercurial/merge.py

@@ -384,7 +384,7 def manifestmerge(repo, wctx, p2, pa, br
     return actions
 
 def actionkey(a):
-    return a[1] == "r" and -1 or 0, a
+    return a[1] in "rf" and -1 or 0, a
 
 def getremove(repo, mctx, overwrite, args):
     """apply usually-non-interactive updates to the working directory

tests/test-add.t

@@ -136,5 +136,23 Issue683: peculiarity with hg revert of
   M a
   A c
   ? a.orig
+  $ hg up -C
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+forget and get should have the right order: added but missing dir should be
+forgotten before file with same name is added
+
+  $ echo file d > d
+  $ hg add d
+  $ hg ci -md
+  $ hg rm d
+  $ mkdir d
+  $ echo a > d/a
+  $ hg add d/a
+  $ rm -r d
+  $ hg up -C
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ cat d
+  file d
 
   $ cd ..