add documentation for mailinfo.scissors and '--no-scissors'

Signed-off-by: Nicolas Sebrecht <nicolas.s.dev@gmx.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-am.txt

@@ -13,7 +13,7 @@ SYNOPSIS
 	 [--3way] [--interactive] [--committer-date-is-author-date]
 	 [--ignore-date] [--ignore-space-change | --ignore-whitespace]
 	 [--whitespace=<option>] [-C<n>] [-p<n>] [--directory=<dir>]
-	 [--reject] [-q | --quiet] [--scissors]
+	 [--reject] [-q | --quiet] [--scissors | --no-scissors]
 	 [<mbox> | <Maildir>...]
 'git am' (--skip | --resolved | --abort)
 
@@ -44,6 +44,9 @@ OPTIONS
 	Remove everything in body before a scissors line (see
 	linkgit:git-mailinfo[1]).
 
+---no-scissors::
+	Ignore scissors lines (see linkgit:git-mailinfo[1]).
+
 -q::
 --quiet::
 	Be quiet. Only print error messages.

Documentation/git-mailinfo.txt

@@ -62,6 +62,11 @@ This is useful if you want to begin your message in a discussion thread
 with comments and suggestions on the message you are responding to, and to
 conclude it with a patch submission, separating the discussion and the
 beginning of the proposed commit log message with a scissors line.
++
+This can enabled by default with the configuration option mailinfo.scissors.
+
+--no-scissors::
+	Ignore scissors lines. Useful for overriding mailinfo.scissors settings.
 
 <msg>::
 	The commit log message extracted from e-mail, usually

builtin-mailinfo.c

@@ -1004,7 +1004,7 @@ static int git_mailinfo_config(const char *var, const char *value, void *unused)
 }
 
 static const char mailinfo_usage[] =
-	"git mailinfo [-k] [-u | --encoding=<encoding> | -n] [--scissors] msg patch < mail >info";
+	"git mailinfo [-k] [-u | --encoding=<encoding> | -n] [--scissors | --no-scissors] msg patch < mail >info";
 
 int cmd_mailinfo(int argc, const char **argv, const char *prefix)
 {