Sort removes first when applying updates (fixes issues 750 and 912)

This change ensures that removes happen first in applyupdates(). This avoids
issues where we try to make a case-only rename of a file on a case insensitive
system. Without this patch, the add of the new name happens before the remove
of the old one - which results in the file not existing, as the two names are
effectively the same.

With the patch, the old name gets removed then the new one gets added, which
is always safe.

mercurial/merge.py

@@ -258,6 +258,17 b' def manifestmerge(repo, p1, p2, pa, over'
 
     return action
 
+def actioncmp(a1, a2):
+    m1 = a1[1]
+    m2 = a2[1]
+    if m1 == m2:
+        return cmp(a1, a2)
+    if m1 == 'r':
+        return -1
+    if m2 == 'r':
+        return 1
+    return cmp(a1, a2)
+
 def applyupdates(repo, action, wctx, mctx):
     "apply the merge action list to the working directory"
 
@@ -265,7 +276,7 b' def applyupdates(repo, action, wctx, mct'
     ms = mergestate(repo)
     ms.reset(wctx.parents()[0].node())
     moves = []
-    action.sort()
+    action.sort(actioncmp)
 
     # prescan for merges
     for a in action:

tests/test-update-reverse.out

@@ -46,9 +46,9 b' resolving manifests'
  side2: remote deleted -> r
  side1: remote deleted -> r
  main: remote created -> g
-getting main
 removing side1
 removing side2
+getting main
 1 files updated, 0 files merged, 2 files removed, 0 files unresolved
 Should only show a main
 a