Remove the bytes between `pos..pos+len` and replace it with the given
data.
+`strbuf_add_commented_lines`::
+
+ Add a NUL-terminated string to the buffer. Each line will be prepended
+ by a comment character and a blank.
+
`strbuf_add`::
Add data of given length to the buffer.
Add a formatted string to the buffer.
+`strbuf_commented_addf`::
+
+ Add a formatted string prepended by a comment character and a
+ blank to the buffer.
+
`strbuf_fread`::
Read a given size of data from a FILE* pointer to the buffer.