Merge branch 'jk/hash-algo-leak-fixes'

Various code paths that initialize a cryptographic hash context but bail out or finish without calling 'git_hash_final()' have been taught to call 'git_hash_discard()' to release allocated resources, fixing memory leaks when Git is built with non-default backends like 'OpenSSL' or 'libgcrypt'. * jk/hash-algo-leak-fixes: hash: add platform-specific discard functions hash: fix memory leak copying sha256 gcrypt handles http: discard hash in dumb-http http_object_request check_stream_oid(): discard hash on read error patch-id: discard hash when done csum-file: provide a function to release checkpoints csum-file: always finalize or discard hash hash: add discard primitive csum-file: drop discard_hashfile()