Documentation: customize diff-options depending on particular command

Customize diff-options depending on particular command as follows,
mostly to make git-diff and git-format-patch manuals less confusing:

* git-format-patch:

  - Mark --patch-with-stat as being the default.

  - Change -p description so that it matches what it actually does and
    so that it doesn't refer to absent "section on generating
    patches".

* git-diff: mark -p as being the default.

* git-diff-index/git-diff-files/git-diff-tree: mark --raw as being
  the default.

Signed-off-by: Sergei Organov <osv@javad.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Sergei Organov

Documentation/diff-options.txt

@@ -1,5 +1,25 @@
+// Please don't remove this comment as asciidoc behaves badly when
+// the first non-empty line is ifdef/ifndef. The symptom is that
+// without this comment the <git-diff-core> attribute conditionally
+// defined below ends up being defined unconditionally.
+// Last checked with asciidoc 7.0.2.
+
+ifndef::git-format-patch[]
+ifndef::git-diff[]
+:git-diff-core: 1
+endif::git-diff[]
+endif::git-format-patch[]
+
+ifdef::git-format-patch[]
 -p::
-	Generate patch (see section on generating patches)
+	Generate patches without diffstat.
+endif::git-format-patch[]
+
+ifndef::git-format-patch[]
+-p::
+	Generate patch (see section on generating patches).
+	{git-diff? This is the default.}
+endif::git-format-patch[]
 
 -u::
 	Synonym for "-p".
@@ -13,6 +33,7 @@
 
 --raw::
 	Generate the raw format.
+	{git-diff-core? This is the default.}
 
 --patch-with-raw::
 	Synonym for "-p --raw".
@@ -41,6 +62,7 @@
 
 --patch-with-stat::
 	Synonym for "-p --stat".
+	{git-format-patch? This is the default.}
 
 -z::
 	NUL-line termination on output.  This affects the --raw

Documentation/git-diff.txt

@@ -75,6 +75,7 @@ and the range notations ("<commit>..<commit>" and
 
 OPTIONS
 -------
+:git-diff: 1
 include::diff-options.txt[]
 
 <path>...::

Documentation/git-format-patch.txt

@@ -66,6 +66,7 @@ reference.
 
 OPTIONS
 -------
+:git-format-patch: 1
 include::diff-options.txt[]
 
 -<n>::