Add helpful buffer shorten function

src/buffer.c

@@ -259,6 +259,15 @@ void git_buf_truncate(git_buf *buf, size_t len)
 	}
 }
 
+void git_buf_shorten(git_buf *buf, size_t amount)
+{
+	if (amount > buf->size)
+		amount = buf->size;
+
+	buf->size = buf->size - amount;
+	buf->ptr[buf->size] = '\0';
+}
+
 void git_buf_rtruncate_at_char(git_buf *buf, char separator)
 {
 	ssize_t idx = git_buf_rfind_next(buf, separator);

src/buffer.h

@@ -91,6 +91,7 @@ int git_buf_vprintf(git_buf *buf, const char *format, va_list ap);
 void git_buf_clear(git_buf *buf);
 void git_buf_consume(git_buf *buf, const char *end);
 void git_buf_truncate(git_buf *buf, size_t len);
+void git_buf_shorten(git_buf *buf, size_t amount);
 void git_buf_rtruncate_at_char(git_buf *path, char separator);
 
 int git_buf_join_n(git_buf *buf, char separator, int nbuf, ...);

src/config_file.c

@@ -1395,7 +1395,7 @@ static int parse_multiline_variable(diskfile_backend *cfg, git_buf *value, int i
 	 * standard, this character **has** to be last one in the buf, with
 	 * no whitespace after it */
 	assert(is_multiline_var(value->ptr));
-	git_buf_truncate(value, git_buf_len(value) - 1);
+	git_buf_shorten(value, 1);
 
 	proc_line = fixup_line(line, in_quotes);
 	if (proc_line == NULL) {

src/indexer.c

@@ -602,7 +602,7 @@ int git_indexer_stream_finalize(git_indexer_stream *idx, git_transfer_progress *
 	git_vector_sort(&idx->objects);
 
 	git_buf_sets(&filename, idx->pack->pack_name);
-	git_buf_truncate(&filename, filename.size - strlen("pack"));
+	git_buf_shorten(&filename, strlen("pack"));
 	git_buf_puts(&filename, "idx");
 	if (git_buf_oom(&filename))
 		return -1;