Write merge strategy into debug logs
Write merge strategy into debug logs

For investigating issues it is sometimes important to know which merge
strategy has been used.

Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>
Change-Id: Icd341cea70059c3d2a7a46edf0c86871daabdfa0

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