diff-merges: introduce log.diffMerges config variable

New log.diffMerges configuration variable sets the format that
--diff-merges=on will be using. The default is "separate".

t4013: add the following tests for log.diffMerges config:

* Test that wrong values are denied.

* Test that the value of log.diffMerges properly affects both
--diff-merges=on and -m.

t9902: fix completion tests for log.d* to match log.diffMerges.

Added documentation for log.diffMerges.

Signed-off-by: Sergey Organov <sorganov@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 26a7b4d19d..87def81699 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -460,6 +460,29 @@ test_expect_success 'log --diff-merges=on matches --diff-merges=separate' '
 	test_cmp expected actual
 '
 
+test_expect_success 'deny wrong log.diffMerges config' '
+	test_config log.diffMerges wrong-value &&
+	test_expect_code 128 git log
+'
+
+test_expect_success 'git config log.diffMerges first-parent' '
+	git log -p --diff-merges=first-parent master >result &&
+	process_diffs result >expected &&
+	test_config log.diffMerges first-parent &&
+	git log -p --diff-merges=on master >result &&
+	process_diffs result >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'git config log.diffMerges first-parent vs -m' '
+	git log -p --diff-merges=first-parent master >result &&
+	process_diffs result >expected &&
+	test_config log.diffMerges first-parent &&
+	git log -p -m master >result &&
+	process_diffs result >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'log -S requires an argument' '
 	test_must_fail git log -S
 '