git-am: add --directory=<dir> option

Thanks to a200337 (git-am: propagate -C<n>, -p<n> options as well,
2008-12-04) and commits around it, "git am" is equipped to correctly
propagate the command line flags such as -C/-p/-whitespace across a patch
failure and restart.

It is trivial to support --directory option now, resurrecting previous
attempts by Kevin and Simon.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-am.sh

@@ -16,6 +16,7 @@ s,signoff       add a Signed-off-by line to the commit message
 u,utf8          recode into utf8 (default)
 k,keep          pass -k flag to git-mailinfo
 whitespace=     pass it through git-apply
+directory=      pass it through git-apply
 C=              pass it through git-apply
 p=              pass it through git-apply
 resolvemsg=     override error message when patch failure occurs
@@ -33,6 +34,14 @@ cd_to_toplevel
 git var GIT_COMMITTER_IDENT >/dev/null ||
 	die "You need to set your committer info first"
 
+sq () {
+	for sqarg
+	do
+		printf "%s" "$sqarg" |
+		sed -e 's/'\''/'\''\'\'''\''/g' -e 's/.*/ '\''&'\''/'
+	done
+}
+
 stop_here () {
     echo "$1" >"$dotest/next"
     exit 1
@@ -155,10 +164,10 @@ do
 		;;
 	--resolvemsg)
 		shift; resolvemsg=$1 ;;
-	--whitespace)
-		git_apply_opt="$git_apply_opt $1=$2"; shift ;;
+	--whitespace|--directory)
+		git_apply_opt="$git_apply_opt $(sq "$1=$2")"; shift ;;
 	-C|-p)
-		git_apply_opt="$git_apply_opt $1$2"; shift ;;
+		git_apply_opt="$git_apply_opt $(sq "$1$2")"; shift ;;
 	--)
 		shift; break ;;
 	*)
@@ -459,7 +468,7 @@ do
 
 	case "$resolved" in
 	'')
-		git apply $git_apply_opt --index "$dotest/patch"
+		eval 'git apply '"$git_apply_opt"' --index "$dotest/patch"'
 		apply_status=$?
 		;;
 	t)