git apply: option to ignore whitespace differences

Introduce --ignore-whitespace option and corresponding config bool to
ignore whitespace differences while applying patches, akin to the
'patch' program.

'git am', 'git rebase' and the bash git completion are made aware of
this option.

Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/git-am.sh b/git-am.sh
index d64d997..ab39b3c 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -16,6 +16,8 @@
 u,utf8          recode into utf8 (default)
 k,keep          pass -k flag to git-mailinfo
 whitespace=     pass it through git-apply
+ignore-space-change pass it through git-apply
+ignore-whitespace pass it through git-apply
 directory=      pass it through git-apply
 C=              pass it through git-apply
 p=              pass it through git-apply
@@ -303,7 +305,7 @@
 		git_apply_opt="$git_apply_opt $(sq "$1$2")"; shift ;;
 	--patch-format)
 		shift ; patch_format="$1" ;;
-	--reject)
+	--reject|--ignore-whitespace|--ignore-space-change)
 		git_apply_opt="$git_apply_opt $1" ;;
 	--committer-date-is-author-date)
 		committer_date_is_author_date=t ;;