Merge branch 'mm/diff-renames-default'

The end-user facing Porcelain level commands like "diff" and "log"
now enables the rename detection by default.

* mm/diff-renames-default:
diff: activate diff.renames by default
log: introduce init_log_defaults()
t: add tests for diff.renames (true/false/unset)
t4001-diff-rename: wrap file creations in a test
Documentation/diff-config: fix description of diff.renames

diff --cc builtin/merge.c
Simple merge

diff --cc diff.c
Simple merge

diff --cc diff.h
Simple merge