Merge branch 'mg/merge-ff-config'

* mg/merge-ff-config:
  tests: check git does not barf on merge.ff values for future versions of git
  merge: introduce merge.ff configuration variable

Conflicts:
	t/t7600-merge.sh

diff --cc builtin/merge.c
Simple merge

diff --cc t/t7600-merge.sh
index a07caa8,8ddaa1d..87aac83
--- 1/t/t7600-merge.sh
--- 2/t/t7600-merge.sh
+++ b/t/t7600-merge.sh
@@@ -28,79 -28,81 +28,80 @@@ Testing basic merge operations/option p
  
  . ./test-lib.sh
  
 -test_expect_success 'set up test data and helpers' '
 -      printf "%s\n" 1 2 3 4 5 6 7 8 9 >file &&
 -      printf "%s\n" "1 X" 2 3 4 5 6 7 8 9 >file.1 &&
 -      printf "%s\n" 1 2 3 4 "5 X" 6 7 8 9 >file.5 &&
 -      printf "%s\n" 1 2 3 4 5 6 7 8 "9 X" >file.9 &&
 -      printf "%s\n" "1 X" 2 3 4 5 6 7 8 9 >result.1 &&
 -      printf "%s\n" "1 X" 2 3 4 "5 X" 6 7 8 9 >result.1-5 &&
 -      printf "%s\n" "1 X" 2 3 4 "5 X" 6 7 8 "9 X" >result.1-5-9 &&
 -      >empty &&
 -
 -      create_merge_msgs() {
 -              echo "Merge commit '\''c2'\''" >msg.1-5 &&
 -              echo "Merge commit '\''c2'\''; commit '\''c3'\''" >msg.1-5-9 &&
 -              {
 -                      echo "Squashed commit of the following:" &&
 -                      echo &&
 -                      git log --no-merges ^HEAD c1
 -              } >squash.1 &&
 -              {
 -                      echo "Squashed commit of the following:" &&
 -                      echo &&
 -                      git log --no-merges ^HEAD c2
 -              } >squash.1-5 &&
 -              {
 -                      echo "Squashed commit of the following:" &&
 -                      echo &&
 -                      git log --no-merges ^HEAD c2 c3
 -              } >squash.1-5-9 &&
 -              echo >msg.nolog &&
 -              {
 -                      echo "* commit '\''c3'\'':" &&
 -                      echo "  commit 3" &&
 -                      echo
 -              } >msg.log
 -      } &&
 -
 -      verify_merge() {
 -              test_cmp "$2" "$1" &&
 -              git update-index --refresh &&
 -              git diff --exit-code &&
 -              if test -n "$3"
 -              then
 -                      git show -s --pretty=format:%s HEAD >msg.act &&
 -                      test_cmp "$3" msg.act
 -              fi
 -      } &&
 -
 -      verify_head() {
 -              echo "$1" >head.expected &&
 -              git rev-parse HEAD >head.actual &&
 -              test_cmp head.expected head.actual
 -      } &&
 -
 -      verify_parents() {
 -              printf "%s\n" "$@" >parents.expected &&
 -              >parents.actual &&
 -              i=1 &&
 -              while test $i -le $#
 -              do
 -                      git rev-parse HEAD^$i >>parents.actual &&
 -                      i=$(expr $i + 1) ||
 -                      return 1
 -              done &&
 -              test_cmp parents.expected parents.actual
 -      } &&
 -
 -      verify_mergeheads() {
 -              printf "%s\n" "$@" >mergehead.expected &&
 -              test_cmp mergehead.expected .git/MERGE_HEAD
 -      } &&
 -
 -      verify_no_mergehead() {
 -              ! test -e .git/MERGE_HEAD
 -      }
 -'
 +printf '%s\n' 1 2 3 4 5 6 7 8 9 >file
 +printf '%s\n' '1 X' 2 3 4 5 6 7 8 9 >file.1
 +printf '%s\n' 1 2 3 4 '5 X' 6 7 8 9 >file.5
 +printf '%s\n' 1 2 3 4 5 6 7 8 '9 X' >file.9
 +printf '%s\n' '1 X' 2 3 4 5 6 7 8 9 >result.1
 +printf '%s\n' '1 X' 2 3 4 '5 X' 6 7 8 9 >result.1-5
 +printf '%s\n' '1 X' 2 3 4 '5 X' 6 7 8 '9 X' >result.1-5-9
++>empty
 +
 +create_merge_msgs () {
 +      echo "Merge commit 'c2'" >msg.1-5 &&
 +      echo "Merge commit 'c2'; commit 'c3'" >msg.1-5-9 &&
 +      {
 +              echo "Squashed commit of the following:" &&
 +              echo &&
 +              git log --no-merges ^HEAD c1
 +      } >squash.1 &&
 +      {
 +              echo "Squashed commit of the following:" &&
 +              echo &&
 +              git log --no-merges ^HEAD c2
 +      } >squash.1-5 &&
 +      {
 +              echo "Squashed commit of the following:" &&
 +              echo &&
 +              git log --no-merges ^HEAD c2 c3
 +      } >squash.1-5-9 &&
 +      echo >msg.nolog &&
 +      {
 +              echo "* commit 'c3':" &&
 +              echo "  commit 3" &&
 +              echo
 +      } >msg.log
 +}
 +
 +verify_merge () {
 +      test_cmp "$2" "$1" &&
 +      git update-index --refresh &&
 +      git diff --exit-code &&
 +      if test -n "$3"
 +      then
 +              git show -s --pretty=format:%s HEAD >msg.act &&
 +              test_cmp "$3" msg.act
 +      fi
 +}
 +
 +verify_head () {
 +      echo "$1" >head.expected &&
 +      git rev-parse HEAD >head.actual &&
 +      test_cmp head.expected head.actual
 +}
 +
 +verify_parents () {
 +      printf '%s\n' "$@" >parents.expected &&
 +      >parents.actual &&
 +      i=1 &&
 +      while test $i -le $#
 +      do
 +              git rev-parse HEAD^$i >>parents.actual &&
 +              i=$(expr $i + 1) ||
 +              return 1
 +      done &&
 +      test_must_fail git rev-parse --verify "HEAD^$i" &&
 +      test_cmp parents.expected parents.actual
 +}
 +
 +verify_mergeheads () {
 +      printf '%s\n' "$@" >mergehead.expected &&
 +      test_cmp mergehead.expected .git/MERGE_HEAD
 +}
 +
 +verify_no_mergehead () {
 +      ! test -e .git/MERGE_HEAD
 +}
  
  test_expect_success 'setup' '
        git add file &&