include sha2.h too where sha1.h is included In preparation for wide sha256 support; stsp@ agrees. Change done mechanically with find . -iname \*.[cy] -exec sam {} + X ,x/<sha1\.h>/i/\n#include <sha2.h>

avoid copying reused deltas to delta cache file; copy from pack file instead ok op@

let callers of got_pack_create() configure rate-limiting of progress reporting Needed by future gotd(8), where progress reports will be sent to a network socket, rather than a local terminal.

move privsep code from pack_create.c into new file pack_create_privsep.c Needed by future gotd(8). ok op@