i18n: git-commit "middle of a merge" message

Gettextize the "You are in the middle of a merge -- cannot amend."
message. Several tests in t7110-reset-merge.sh explicitly checked for
this message. Change them to skip under GETTEXT_POISON=YesPlease.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -928,9 +928,9 @@ static int parse_and_validate_options(int argc, const char *argv[],
 	if (amend && initial_commit)
 		die(_("You have nothing to amend."));
 	if (amend && in_merge)
-		die("You are in the middle of a merge -- cannot amend.");
+		die(_("You are in the middle of a merge -- cannot amend."));
 	if (fixup_message && squash_message)
-		die("Options --squash and --fixup cannot be used together");
+		die(_("Options --squash and --fixup cannot be used together"));
 	if (use_message)
 		f++;
 	if (edit_message)

t/t7110-reset-merge.sh

@@ -233,7 +233,7 @@ test_expect_success '"reset --merge HEAD^" is ok with pending merge' '
 #           working index HEAD target         working index HEAD
 #           ----------------------------------------------------
 # file1:     X       U     B    C     --keep   (disallowed)
-test_expect_success '"reset --keep HEAD^" fails with pending merge' '
+test_expect_success C_LOCALE_OUTPUT '"reset --keep HEAD^" fails with pending merge' '
     git reset --hard third &&
     test_must_fail git merge branch1 &&
     test_must_fail git reset --keep HEAD^ 2>err.log &&
@@ -259,7 +259,7 @@ test_expect_success '"reset --merge HEAD" is ok with pending merge' '
 #           working index HEAD target         working index HEAD
 #           ----------------------------------------------------
 # file1:     X       U     B    B     --keep   (disallowed)
-test_expect_success '"reset --keep HEAD" fails with pending merge' '
+test_expect_success C_LOCALE_OUTPUT '"reset --keep HEAD" fails with pending merge' '
     git reset --hard third &&
     test_must_fail git merge branch1 &&
     test_must_fail git reset --keep HEAD 2>err.log &&
@@ -280,7 +280,7 @@ test_expect_success '--merge is ok with added/deleted merge' '
     git diff --exit-code --cached
 '
 
-test_expect_success '--keep fails with added/deleted merge' '
+test_expect_success C_LOCALE_OUTPUT '--keep fails with added/deleted merge' '
     git reset --hard third &&
     rm -f file2 &&
     test_must_fail git merge branch3 &&