Merge branch 'ps/apply-leakfix'

"git apply" had custom buffer management code that predated before use of strbuf got widespread, which has been updated to use strbuf, which also plugged some memory leaks. * ps/apply-leakfix: apply: refactor `struct image` to use a `struct strbuf` apply: rename members that track line count and allocation length apply: refactor code to drop `line_allocated` apply: introduce macro and function to init images apply: rename functions operating on `struct image` apply: reorder functions to move image-related things together