[RFC PATCH 1/1] for-each-ref: do not output empty lines

[Eric Freese <ericdfreese@gmail.com>]

If the format string expands to an empty string for a given ref, do not
print the empty line.

This is helpful when wanting to print only certain kinds of refs that
you can't already filter for.

For example, to exclude symbolic refs, use format string:
  "%(if)%(symref)%(then)%(else)%(refname)%(end)"

Or to include only symbolic refs, use:
  "%(if)%(symref)%(then)%(refname)%(end)"

Signed-off-by: Eric Freese <ericdfreese@gmail.com>
---
 ref-filter.c            | 3 ++-
 t/t6300-for-each-ref.sh | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/ref-filter.c b/ref-filter.c
index 7338cfc671..b5b3c4ddf6 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -2395,9 +2395,10 @@ void show_ref_array_item(struct ref_array_item *info,
 	if (format_ref_array_item(info, format, &final_buf, &error_buf))
 		die("%s", error_buf.buf);
 	fwrite(final_buf.buf, 1, final_buf.len, stdout);
+	if (final_buf.len)
+		putchar('\n');
 	strbuf_release(&error_buf);
 	strbuf_release(&final_buf);
-	putchar('\n');
 }
 
 void pretty_print_ref(const char *name, const struct object_id *oid,
diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index 9c910ce746..1f070e63e2 100755
--- a/t/t6300-for-each-ref.sh
+++ b/t/t6300-for-each-ref.sh
@@ -42,7 +42,7 @@ test_atom() {
 		 sym) ref=refs/heads/sym ;;
 		   *) ref=$1 ;;
 	esac
-	printf '%s\n' "$3" >expected
+	{ test -n "$3" && printf '%s\n' "$3"; } >expected
 	test_expect_${4:-success} $PREREQ "basic atom: $1 $2" "
 		git for-each-ref --format='%($2)' $ref >actual &&
 		sanitize_pgp <actual >actual.clean &&
@@ -313,7 +313,7 @@ test_expect_success 'Check format of strftime-local date fields' '
 '
 
 test_expect_success 'exercise strftime with odd fields' '
-	echo >expected &&
+	>expected &&
 	git for-each-ref --format="%(authordate:format:)" refs/heads >actual &&
 	test_cmp expected actual &&
 	long="long format -- $ZERO_OID$ZERO_OID$ZERO_OID$ZERO_OID$ZERO_OID$ZERO_OID$ZERO_OID" &&
-- 
2.23.0