Add --summary to git-format-patch by default

This adds --summary output in addition to the --stat to the
output from git-format-patch by default.

I think additions, removals and filemode changes are rare but
notable events and always showing it makes sense.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-log.c

@@ -468,7 +468,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		die ("unrecognized argument: %s", argv[1]);
 
 	if (!rev.diffopt.output_format)
-		rev.diffopt.output_format = DIFF_FORMAT_DIFFSTAT | DIFF_FORMAT_PATCH;
+		rev.diffopt.output_format = DIFF_FORMAT_DIFFSTAT | DIFF_FORMAT_SUMMARY | DIFF_FORMAT_PATCH;
 
 	if (!output_directory)
 		output_directory = prefix;

t/t4013/diff.format-patch_--attach_--stdout_initial..master

@@ -19,6 +19,7 @@ This is the second commit.
  file0   |    3 +++
  file2   |    3 ---
  3 files changed, 5 insertions(+), 3 deletions(-)
+ delete mode 100644 file2
 --------------g-i-t--v-e-r-s-i-o-n
 Content-Type: text/x-patch;
  name="1bde4ae5f36c8d9abe3a0fce0c6aab3c4a12fe44.diff"
@@ -77,6 +78,7 @@ Content-Transfer-Encoding: 8bit
  dir/sub |    2 ++
  file1   |    3 +++
  2 files changed, 5 insertions(+), 0 deletions(-)
+ create mode 100644 file1
 --------------g-i-t--v-e-r-s-i-o-n
 Content-Type: text/x-patch;
  name="9a6d4949b6b76956d9d5e26f2791ec2ceff5fdc0.diff"
@@ -126,6 +128,7 @@ Content-Transfer-Encoding: 8bit
  file0   |    3 +++
  file3   |    4 ++++
  3 files changed, 9 insertions(+), 0 deletions(-)
+ create mode 100644 file3
 --------------g-i-t--v-e-r-s-i-o-n
 Content-Type: text/x-patch;
  name="c7a2ab9e8eac7b117442a607d5a9b3950ae34d5a.diff"

t/t4013/diff.format-patch_--attach_--stdout_initial..master^

@@ -19,6 +19,7 @@ This is the second commit.
  file0   |    3 +++
  file2   |    3 ---
  3 files changed, 5 insertions(+), 3 deletions(-)
+ delete mode 100644 file2
 --------------g-i-t--v-e-r-s-i-o-n
 Content-Type: text/x-patch;
  name="1bde4ae5f36c8d9abe3a0fce0c6aab3c4a12fe44.diff"
@@ -77,6 +78,7 @@ Content-Transfer-Encoding: 8bit
  dir/sub |    2 ++
  file1   |    3 +++
  2 files changed, 5 insertions(+), 0 deletions(-)
+ create mode 100644 file1
 --------------g-i-t--v-e-r-s-i-o-n
 Content-Type: text/x-patch;
  name="9a6d4949b6b76956d9d5e26f2791ec2ceff5fdc0.diff"

t/t4013/diff.format-patch_--attach_--stdout_initial..side

@@ -17,6 +17,7 @@ Content-Transfer-Encoding: 8bit
  file0   |    3 +++
  file3   |    4 ++++
  3 files changed, 9 insertions(+), 0 deletions(-)
+ create mode 100644 file3
 --------------g-i-t--v-e-r-s-i-o-n
 Content-Type: text/x-patch;
  name="c7a2ab9e8eac7b117442a607d5a9b3950ae34d5a.diff"

t/t4013/diff.format-patch_--stdout_initial..master

@@ -10,6 +10,7 @@ This is the second commit.
  file0   |    3 +++
  file2   |    3 ---
  3 files changed, 5 insertions(+), 3 deletions(-)
+ delete mode 100644 file2
 
 diff --git a/dir/sub b/dir/sub
 index 35d242b..8422d40 100644
@@ -53,6 +54,7 @@ Subject: [PATCH] Third
  dir/sub |    2 ++
  file1   |    3 +++
  2 files changed, 5 insertions(+), 0 deletions(-)
+ create mode 100644 file1
 
 diff --git a/dir/sub b/dir/sub
 index 8422d40..cead32e 100644
@@ -87,6 +89,7 @@ Subject: [PATCH] Side
  file0   |    3 +++
  file3   |    4 ++++
  3 files changed, 9 insertions(+), 0 deletions(-)
+ create mode 100644 file3
 
 diff --git a/dir/sub b/dir/sub
 index 35d242b..7289e35 100644

t/t4013/diff.format-patch_--stdout_initial..master^

@@ -10,6 +10,7 @@ This is the second commit.
  file0   |    3 +++
  file2   |    3 ---
  3 files changed, 5 insertions(+), 3 deletions(-)
+ delete mode 100644 file2
 
 diff --git a/dir/sub b/dir/sub
 index 35d242b..8422d40 100644
@@ -53,6 +54,7 @@ Subject: [PATCH] Third
  dir/sub |    2 ++
  file1   |    3 +++
  2 files changed, 5 insertions(+), 0 deletions(-)
+ create mode 100644 file1
 
 diff --git a/dir/sub b/dir/sub
 index 8422d40..cead32e 100644

t/t4013/diff.format-patch_--stdout_initial..side

@@ -9,6 +9,7 @@ Subject: [PATCH] Side
  file0   |    3 +++
  file3   |    4 ++++
  3 files changed, 9 insertions(+), 0 deletions(-)
+ create mode 100644 file3
 
 diff --git a/dir/sub b/dir/sub
 index 35d242b..7289e35 100644