make git_diff_stats_to_buf not show 0 insertions or 0 deletions

src/diff_stats.c

@@ -299,15 +299,24 @@ int git_diff_stats_to_buf(
 	}
 
 	if (format & GIT_DIFF_STATS_FULL || format & GIT_DIFF_STATS_SHORT) {
-		error = git_buf_printf(
-			out, " %" PRIuZ " file%s changed, %" PRIuZ
-			" insertion%s(+), %" PRIuZ " deletion%s(-)\n",
-			stats->files_changed, stats->files_changed != 1 ? "s" : "",
-			stats->insertions, stats->insertions != 1 ? "s" : "",
-			stats->deletions, stats->deletions != 1 ? "s" : "");
+		git_buf_printf(
+			out, " %" PRIuZ " file%s changed",
+			stats->files_changed, stats->files_changed != 1 ? "s" : "");
 
-		if (error < 0)
-			return error;
+		if (stats->insertions || stats->deletions == 0)
+			git_buf_printf(
+				out, ", %" PRIuZ " insertion%s(+)",
+				stats->insertions, stats->insertions != 1 ? "s" : "");
+
+		if (stats->deletions || stats->insertions == 0)
+			git_buf_printf(
+				out, ", %" PRIuZ " deletion%s(-)",
+				stats->deletions, stats->deletions != 1 ? "s" : "");
+
+		git_buf_putc(out, '\n');
+
+		if (git_buf_oom(out))
+			return -1;
 	}
 
 	if (format & GIT_DIFF_STATS_INCLUDE_SUMMARY) {
@@ -333,4 +342,3 @@ void git_diff_stats_free(git_diff_stats *stats)
 	git__free(stats->filestats);
 	git__free(stats);
 }
-

tests/diff/format_email.c

@@ -112,7 +112,7 @@ void test_diff_format_email__with_message(void)
 	"Also test if new paragraphs are included correctly.\n" \
 	"---\n" \
 	" file3.txt | 1 +\n" \
-	" 1 file changed, 1 insertion(+), 0 deletions(-)\n" \
+	" 1 file changed, 1 insertion(+)\n" \
 	"\n" \
 	"diff --git a/file3.txt b/file3.txt\n" \
 	"index 9a2d780..7309653 100644\n" \
@@ -155,7 +155,7 @@ void test_diff_format_email__multiple(void)
 	"---\n" \
 	" file2.txt | 5 +++++\n" \
 	" file3.txt | 5 +++++\n" \
-	" 2 files changed, 10 insertions(+), 0 deletions(-)\n" \
+	" 2 files changed, 10 insertions(+)\n" \
 	" create mode 100644 file2.txt\n" \
 	" create mode 100644 file3.txt\n" \
 	"\n" \

tests/diff/stats.c

@@ -113,6 +113,42 @@ void test_diff_stats__shortstat(void)
 	git_buf_free(&buf);
 }
 
+void test_diff_stats__shortstat_noinsertions(void)
+{
+	git_buf buf = GIT_BUF_INIT;
+	const char *stat =
+	" 1 file changed, 2 deletions(-)\n";
+
+	diff_stats_from_commit_oid(
+		&_stats, "06b7b69a62cbd1e53c6c4e0c3f16473dcfdb4af6", false);
+
+	cl_assert_equal_sz(1, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(0, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(2, git_diff_stats_deletions(_stats));
+
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_SHORT, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
+	git_buf_free(&buf);
+}
+
+void test_diff_stats__shortstat_nodeletions(void)
+{
+	git_buf buf = GIT_BUF_INIT;
+	const char *stat =
+	" 1 file changed, 3 insertions(+)\n";
+
+	diff_stats_from_commit_oid(
+		&_stats, "5219b9784f9a92d7bd7cb567a6d6a21bfb86697e", false);
+
+	cl_assert_equal_sz(1, git_diff_stats_files_changed(_stats));
+	cl_assert_equal_sz(3, git_diff_stats_insertions(_stats));
+	cl_assert_equal_sz(0, git_diff_stats_deletions(_stats));
+
+	cl_git_pass(git_diff_stats_to_buf(&buf, _stats, GIT_DIFF_STATS_SHORT, 0));
+	cl_assert_equal_s(stat, git_buf_cstr(&buf));
+	git_buf_free(&buf);
+}
+
 void test_diff_stats__rename(void)
 {
 	git_buf buf = GIT_BUF_INIT;

tests/resources/diff_format_email/.gitted/refs/heads/master

@@ -1 +1 @@
-627e7e12d87e07a83fad5b6bfa25e86ead4a5270
+5219b9784f9a92d7bd7cb567a6d6a21bfb86697e

tests/resources/diff_format_email/file3.txt

@@ -4,3 +4,4 @@ file3
 file3
 file3
 file3
+file3