unpack-trees: print "Aborting" to stderr

display_error_msgs() prints all the errors to stderr already (if any),
followed by "Aborting" (if any) to stdout. Make the latter go to stderr
instead.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Michael J Gruber

t/t7607-merge-overwrite.sh

@@ -107,6 +107,7 @@ error: The following untracked working tree files would be overwritten by merge:
 	sub
 	sub2
 Please move or remove them before you can merge.
+Aborting
 EOF
 
 test_expect_success 'will not overwrite untracked file in leading path' '

t/t7609-merge-co-error-msgs.sh

@@ -32,6 +32,7 @@ error: The following untracked working tree files would be overwritten by merge:
 	three
 	two
 Please move or remove them before you can merge.
+Aborting
 EOF
 
 test_expect_success 'untracked files overwritten by merge (fast and non-fast forward)' '
@@ -56,6 +57,7 @@ Please, commit your changes or stash them before you can merge.
 error: The following untracked working tree files would be overwritten by merge:
 	five
 Please move or remove them before you can merge.
+Aborting
 EOF
 
 test_expect_success 'untracked files or local changes ovewritten by merge' '
@@ -71,6 +73,7 @@ error: Your local changes to the following files would be overwritten by checkou
 	rep/one
 	rep/two
 Please, commit your changes or stash them before you can switch branches.
+Aborting
 EOF
 
 test_expect_success 'cannot switch branches because of local changes' '
@@ -92,6 +95,7 @@ error: Your local changes to the following files would be overwritten by checkou
 	rep/one
 	rep/two
 Please, commit your changes or stash them before you can switch branches.
+Aborting
 EOF
 
 test_expect_success 'not uptodate file porcelain checkout error' '
@@ -105,6 +109,7 @@ error: Updating the following directories would lose untracked files in it:
 	rep
 	rep2
 
+Aborting
 EOF
 
 test_expect_success 'not_uptodate_dir porcelain checkout error' '

unpack-trees.c

@@ -159,7 +159,7 @@ static void display_error_msgs(struct unpack_trees_options *o)
 		string_list_clear(rejects, 0);
 	}
 	if (something_displayed)
-		printf("Aborting\n");
+		fprintf(stderr, "Aborting\n");
 }
 
 /*