[PATCH] rev-list: use hdr_termination instead of a always using a newline

[Jacob Keller <jacob.e.keller@intel.com>]

From: Jacob Keller <jacob.keller@gmail.com>

When adding support for prefixing output of log and other commands using
--line-prefix, commit 660e113ce118 ("graph: add support for
--line-prefix on all graph-aware output", 2016-08-31) accidentally
broke rev-list --header output.

In order to make the output appear with a line-prefix, the flow was
changed to always use the graph subsystem for display. Unfortunately
the graph flow in rev-list did not use info->hdr_termination as it was
assumed that graph output would never need to putput NULs.

Since we now always use the graph code in order to handle the case of
line-prefix, simply replace putchar('\n') with
putchar(info->hdr_termination) which will correct this issue.

Add a test for the --header case to make sure we don't break it in the
future. Implement a helper function test_ends_with_nul() to make it more
obvious what sort of check we are looking for.

Reported-by: Dennis Kaarsemaker <dennis@kaarsemaker.net>
Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
---

Here's my solution, with an updated test using a helper function based
on using sed (which I think is more portable than tail -n1 ?). The
change actually is very simple. I ran the test suite and it appears to
be not breaking anyone else since the normal case is
hdr_termination="\n" except in the cases where it needs to be NUL.

Thanks for the bug report!

 builtin/rev-list.c       |  2 +-
 t/t6000-rev-list-misc.sh | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index 8479f6ed28aa..c43decda7011 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -145,7 +145,7 @@ static void show_commit(struct commit *commit, void *data)
 			 */
 			if (buf.len && buf.buf[buf.len - 1] == '\n')
 				graph_show_padding(revs->graph);
-			putchar('\n');
+			putchar(info->hdr_termination);
 		} else {
 			/*
 			 * If the message buffer is empty, just show
diff --git a/t/t6000-rev-list-misc.sh b/t/t6000-rev-list-misc.sh
index 3e752ce03280..e8c6979baf59 100755
--- a/t/t6000-rev-list-misc.sh
+++ b/t/t6000-rev-list-misc.sh
@@ -4,6 +4,12 @@ test_description='miscellaneous rev-list tests'
 
 . ./test-lib.sh
 
+test_ends_with_nul() {
+	printf "\0" >nul
+	sed '$!d' "$@" >contents
+	test_cmp_bin nul contents
+}
+
 test_expect_success setup '
 	echo content1 >wanted_file &&
 	echo content2 >unwanted_file &&
@@ -100,4 +106,9 @@ test_expect_success '--bisect and --first-parent can not be combined' '
 	test_must_fail git rev-list --bisect --first-parent HEAD
 '
 
+test_expect_success '--header shows a NUL after each commit' '
+	git rev-list --header --max-count=1 HEAD | sed \$!d >actual &&
+	test_ends_with_nul actual
+'
+
 test_done
-- 
2.10.0.560.g867c144