git-format-patch: the default suffix is now .patch, not .txt

Editors often give easier handling of patch files if the
filename ends with .patch, so use it instead of .txt.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/git-format-patch.txt

@@ -81,9 +81,9 @@ OPTIONS
 	provide a new patch series.
 
 --suffix=.<sfx>::
-	Instead of using `.txt` as the suffix for generated
+	Instead of using `.patch` as the suffix for generated
 	filenames, use specifed suffix.  A common alternative is
-	`--suffix=.patch`.
+	`--suffix=.txt`.
 +
 Note that you would need to include the leading dot `.` if you
 want a filename like `0001-description-of-my-change.patch`, and
@@ -93,15 +93,14 @@ not add any suffix.
 CONFIGURATION
 -------------
 You can specify extra mail header lines to be added to each
-message in the repository configuration as follows:
+message in the repository configuration.  Also you can specify
+the default suffix different from the built-in one:
 
+------------
 [format]
         headers = "Organization: git-foo\n"
-
-You can specify default suffix used:
-
-[format]
-        suffix = .patch
+        suffix = .txt
+------------
 
 
 EXAMPLES

Documentation/howto/rebase-from-internal-branch.txt

@@ -106,7 +106,7 @@ prepare #2 and #3 for e-mail submission.
 
     $ git format-patch master^^ master
 
-This creates two files, 0001-XXXX.txt and 0002-XXXX.txt.  Send
+This creates two files, 0001-XXXX.patch and 0002-XXXX.patch.  Send
 them out "To: " your project maintainer and "Cc: " your mailing
 list.  You could use contributed script git-send-email if
 your host has necessary perl modules for this, but your usual

builtin-log.c

@@ -197,7 +197,7 @@ static int istitlechar(char c)
 
 static char *extra_headers = NULL;
 static int extra_headers_size = 0;
-static const char *fmt_patch_suffix = ".txt";
+static const char *fmt_patch_suffix = ".patch";
 
 static int git_format_config(const char *var, const char *value)
 {