merge: do early copy to deal with issue636 Without copies/renames, merges source names are 1:1 with their targets. Copies and renames introduce the possibility that there will be two merges with the same input but different output. By doing the copy to the destination name before the merge, the actual merge becomes 1:1 again, and no source is the input to two different merges. - add a preliminary scan to applyupdates to do copies - for the merge action, pass the old name (for finding ancestors) and the new name (for input to the merge) to filemerge - eliminate the old post-merge copy - lookup file contents from new name in filemerge - pass new name to external merge helper - report merge failure at new name - add a test

1 files updated, 0 files merged, 0 files removed, 0 files unresolved
pulling from ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
merging testdir/subdir/a and testdir/a
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
M testdir/subdir/a
diff -r d02b3fc32762 testdir/subdir/a
--- a/testdir/subdir/a
+++ b/testdir/subdir/a
@@ -1,1 +1,1 @@ a
-a
+alpha