MINOR: ist: Rename istappend() to __istappend()
Indicate that this function is not inherently safe by adding two underscores as
a prefix.
diff --git a/include/import/ist.h b/include/import/ist.h
index daf23d5..a19e228 100644
--- a/include/import/ist.h
+++ b/include/import/ist.h
@@ -425,7 +425,7 @@
/* appends <src> after <dst>. The caller must ensure that the underlying buffer
* is large enough to fit the character.
*/
-static inline struct ist istappend(struct ist dst, const char src)
+static inline struct ist __istappend(struct ist dst, const char src)
{
dst.ptr[dst.len++] = src;