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

#!/bin/sh

hg init
touch a
hg add a
hg commit -m "Added a" -d "1000000 0"

touch main
hg add main
hg commit -m "Added main" -d "1000000 0"
hg checkout 0

echo Main should be gone
ls

touch side1
hg add side1
hg commit -m "Added side1" -d "1000000 0"
touch side2
hg add side2
hg commit -m "Added side2" -d "1000000 0"

hg log

echo Should have two heads, side2 and main
hg heads

echo Should show "a side1 side2"
ls

hg update --debug -C 1
echo Should only show "a main"
ls