simplemerge: move printing of merge result to extension...
simplemerge: move printing of merge result to extension
The `mercurial.simplemerge` module still has some command-lines
processing that doesn't belong in such a low-level module. This patch
moves the handling of `hg simplemerge --print` to the extension by
having `mercurial.simplemerge.simplemerge()` return the merged text.
Differential Revision:
https://phab.mercurial-scm.org/D12148
