Merge branch 'so/log-diff-merges-opt'

Earlier, to countermand the implicit "-m" option when the
"--first-parent" option is used with "git log", we added the
"--[no-]diff-merges" option in the jk/log-fp-implies-m topic.  To
leave the door open to allow the "--diff-merges" option to take
values that instructs how patches for merge commits should be
computed (e.g. "cc"? "-p against first parent?"), redefine
"--diff-merges" to take non-optional value, and implement "off"
that means the same thing as "--no-diff-merges".

* so/log-diff-merges-opt:
  t/t4013: add test for --diff-merges=off
  doc/git-log: describe --diff-merges=off
  revision: change "--diff-merges" option to require parameter

diff --cc Documentation/git-log.txt
Simple merge

diff --cc revision.c
Simple merge

diff --cc t/t4013-diff-various.sh
Simple merge

diff --cc t/t4013/diff.log_--diff-merges=off_-p_--first-parent_master
index 0000000000000000000000000000000000000000,c878f13c95194a2f49762c3744f97ba5a4c3c193..194e893c94f861080558e9cec4f0de6a021abd5f
mode 000000,100644..100644
--- /dev/null
--- 2/t/t4013/diff.log_--diff-merges=off_-p_--first-parent_master
+++ b/t/t4013/diff.log_--diff-merges=off_-p_--first-parent_master
@@@ -1,0 -1,78 +1,78 @@@
 -    Merge branch 'side' into master
+ $ git log --diff-merges=off -p --first-parent master
+ commit 59d314ad6f356dd08601a4cd5e530381da3e3c64
+ Merge: 9a6d494 c7a2ab9
+ Author: A U Thor <author@example.com>
+ Date:   Mon Jun 26 00:04:00 2006 +0000
+ 
++    Merge branch 'side'
+ 
+ commit 9a6d4949b6b76956d9d5e26f2791ec2ceff5fdc0
+ Author: A U Thor <author@example.com>
+ Date:   Mon Jun 26 00:02:00 2006 +0000
+ 
+     Third
+ 
+ diff --git a/dir/sub b/dir/sub
+ index 8422d40..cead32e 100644
+ --- a/dir/sub
+ +++ b/dir/sub
+ @@ -2,3 +2,5 @@ A
+  B
+  C
+  D
+ +E
+ +F
+ diff --git a/file1 b/file1
+ new file mode 100644
+ index 0000000..b1e6722
+ --- /dev/null
+ +++ b/file1
+ @@ -0,0 +1,3 @@
+ +A
+ +B
+ +C
+ 
+ commit 1bde4ae5f36c8d9abe3a0fce0c6aab3c4a12fe44
+ Author: A U Thor <author@example.com>
+ Date:   Mon Jun 26 00:01:00 2006 +0000
+ 
+     Second
+     
+     This is the second commit.
+ 
+ diff --git a/dir/sub b/dir/sub
+ index 35d242b..8422d40 100644
+ --- a/dir/sub
+ +++ b/dir/sub
+ @@ -1,2 +1,4 @@
+  A
+  B
+ +C
+ +D
+ diff --git a/file0 b/file0
+ index 01e79c3..b414108 100644
+ --- a/file0
+ +++ b/file0
+ @@ -1,3 +1,6 @@
+  1
+  2
+  3
+ +4
+ +5
+ +6
+ diff --git a/file2 b/file2
+ deleted file mode 100644
+ index 01e79c3..0000000
+ --- a/file2
+ +++ /dev/null
+ @@ -1,3 +0,0 @@
+ -1
+ -2
+ -3
+ 
+ commit 444ac553ac7612cc88969031b02b3767fb8a353a
+ Author: A U Thor <author@example.com>
+ Date:   Mon Jun 26 00:00:00 2006 +0000
+ 
+     Initial
+ $

diff --cc t/t4013/diff.log_--first-parent_--diff-merges=off_-p_master
index 0000000000000000000000000000000000000000,ad2e6d3be22cca4383d4adc1be04aa578d1eeee5..5d7461a167ee1662b4b133105e2e3c81e4f1b7d5
mode 000000,100644..100644
--- /dev/null
--- 2/t/t4013/diff.log_--first-parent_--diff-merges=off_-p_master
+++ b/t/t4013/diff.log_--first-parent_--diff-merges=off_-p_master
@@@ -1,0 -1,78 +1,78 @@@
 -    Merge branch 'side' into master
+ $ git log --first-parent --diff-merges=off -p master
+ commit 80e25ffa65bcdbe82ef654b4d06dbbde7945c37f
+ Merge: 9a6d494 c7a2ab9
+ Author: A U Thor <author@example.com>
+ Date:   Mon Jun 26 00:04:00 2006 +0000
+ 
++    Merge branch 'side'
+ 
+ commit 9a6d4949b6b76956d9d5e26f2791ec2ceff5fdc0
+ Author: A U Thor <author@example.com>
+ Date:   Mon Jun 26 00:02:00 2006 +0000
+ 
+     Third
+ 
+ diff --git a/dir/sub b/dir/sub
+ index 8422d40..cead32e 100644
+ --- a/dir/sub
+ +++ b/dir/sub
+ @@ -2,3 +2,5 @@ A
+  B
+  C
+  D
+ +E
+ +F
+ diff --git a/file1 b/file1
+ new file mode 100644
+ index 0000000..b1e6722
+ --- /dev/null
+ +++ b/file1
+ @@ -0,0 +1,3 @@
+ +A
+ +B
+ +C
+ 
+ commit 1bde4ae5f36c8d9abe3a0fce0c6aab3c4a12fe44
+ Author: A U Thor <author@example.com>
+ Date:   Mon Jun 26 00:01:00 2006 +0000
+ 
+     Second
+     
+     This is the second commit.
+ 
+ diff --git a/dir/sub b/dir/sub
+ index 35d242b..8422d40 100644
+ --- a/dir/sub
+ +++ b/dir/sub
+ @@ -1,2 +1,4 @@
+  A
+  B
+ +C
+ +D
+ diff --git a/file0 b/file0
+ index 01e79c3..b414108 100644
+ --- a/file0
+ +++ b/file0
+ @@ -1,3 +1,6 @@
+  1
+  2
+  3
+ +4
+ +5
+ +6
+ diff --git a/file2 b/file2
+ deleted file mode 100644
+ index 01e79c3..0000000
+ --- a/file2
+ +++ /dev/null
+ @@ -1,3 +0,0 @@
+ -1
+ -2
+ -3
+ 
+ commit 444ac553ac7612cc88969031b02b3767fb8a353a
+ Author: A U Thor <author@example.com>
+ Date:   Mon Jun 26 00:00:00 2006 +0000
+ 
+     Initial
+ $