git-am: rename apply_opt_extra file to apply-opt

All other state files use dash in their names, not underscores.
Also, there is no reason to call this "extra".  Drop it.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

git-am.sh

@@ -250,7 +250,7 @@ else
 	# -s, -u, -k, --whitespace, -3, -C and -p flags are kept
 	# for the resuming session after a patch failure.
 	# -i can and must be given when resuming.
-	echo " $git_apply_opt" >"$dotest/apply_opt_extra"
+	echo " $git_apply_opt" >"$dotest/apply-opt"
 	echo "$threeway" >"$dotest/threeway"
 	echo "$sign" >"$dotest/sign"
 	echo "$utf8" >"$dotest/utf8"
@@ -288,7 +288,7 @@ if test "$(cat "$dotest/threeway")" = t
 then
 	threeway=t
 fi
-git_apply_opt=$(cat "$dotest/apply_opt_extra")
+git_apply_opt=$(cat "$dotest/apply-opt")
 if test "$(cat "$dotest/sign")" = t
 then
 	SIGNOFF=`git var GIT_COMMITTER_IDENT | sed -e '

t/t4252-am-options.sh

@@ -45,7 +45,6 @@ test_expect_success 'interrupted am -C1 -p2' '
 	rm -rf .git/rebase-apply &&
 	git reset --hard initial &&
 	test_must_fail git am -p2 -C1 "$tm"/am-test-4-? &&
-	cat .git/rebase-apply/apply_opt_extra &&
 	git am --skip &&
 	grep 3 file-1 &&
 	grep "^Three$" file-2