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

Documentation/git-log.txt

@@ -148,7 +148,6 @@ combined-diff option or with `--no-diff-merges`).
 	rename or copy detection have been requested).
 
 -m::
---diff-merges::
 	This flag makes the merge commits show the full diff like
 	regular commits; for each merge parent, a separate log entry
 	and diff is generated. An exception is that only diff against
@@ -156,6 +155,11 @@ combined-diff option or with `--no-diff-merges`).
 	in that case, the output represents the changes the merge
 	brought _into_ the then-current branch.
 
+--diff-merges=off::
+--no-diff-merges::
+	Disable output of diffs for merge commits (default). Useful to
+	override `-m`, `-c`, or `--cc`.
+
 :git-log: 1
 include::diff-options.txt[]
 

revision.c

@@ -2343,8 +2343,15 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->diff = 1;
 		revs->diffopt.flags.recursive = 1;
 		revs->diffopt.flags.tree_in_recursive = 1;
-	} else if (!strcmp(arg, "-m") || !strcmp(arg, "--diff-merges")) {
+	} else if (!strcmp(arg, "-m")) {
 		revs->ignore_merges = 0;
+	} else if ((argcount = parse_long_opt("diff-merges", argv, &optarg))) {
+		if (!strcmp(optarg, "off")) {
+			revs->ignore_merges = 1;
+		} else {
+			die(_("unknown value for --diff-merges: %s"), optarg);
+		}
+		return argcount;
 	} else if (!strcmp(arg, "--no-diff-merges")) {
 		revs->ignore_merges = 1;
 	} else if (!strcmp(arg, "-c")) {

t/t4013-diff-various.sh

@@ -298,6 +298,8 @@ log --root -c --patch-with-stat --summary master
 # improved by Timo's patch
 log --root --cc --patch-with-stat --summary master
 log --no-diff-merges -p --first-parent master
+log --diff-merges=off -p --first-parent master
+log --first-parent --diff-merges=off -p master
 log -p --first-parent master
 log -m -p --first-parent master
 log -m -p master

t/t4013/diff.log_--diff-merges=off_-p_--first-parent_master

@@ -0,0 +1,78 @@
+$ 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
+$

t/t4013/diff.log_--first-parent_--diff-merges=off_-p_master

@@ -0,0 +1,78 @@
+$ 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
+$