fixes send.sh test fallout on arm64 and should also fix i386 ok op@

ok op

This adds a set of functions to abstract over SHA1Init, SHA1Update, SHA1Final, their respective SHA256 variants and how to compare digests. Replace all the SHA1*() usage with the new APIs. It's a preparatory step for sha256 handling. ok stsp@

it abstracts over the hash type and ensures that object ids are zero'ed before their sha1 digest is written. Needed by the incoming sha256 support. ok stsp@

It will soon grow functions to deal with sha256 too. stsp@ agrees.

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>

Patch by Josiah Frentsos, thanks!

Don't assume commit info is always written. This is only true when diffing a commit against (one of) its direct parent(s). Otherwise we perform an invalid read on a tmp got_diff_line array and end up passing bogus offsets to fseeko(). Bug found and fixed by stsp with a minor tweak by me. ok jamsek for stsp's initial diff ok stsp@

This fixes the (harmless) errors raised by gitconfig.c on indented comment lines and adds a test case for it. Reported by James Cook, thanks! ok stsp@

The first example is meant to show the default values for all the options. Sync with reality.

cmd_merge is the only subcommand that may create commits that doesn't parse the git config files, thusly failing for users without GOT_AUTHOR defined. Problem reported by James Cook who also provided an initial test case, thanks! ok jamsek

Do not assume that remote repositories will always have our objects. In Git protocol terms: Do not wait for an ACK from the server before sending the final "done" message. Otherwise servers might be waiting for more have-lines from us in order to find a common ancestor, which will never be sent by us. Problem reported by James Cook who also provided an initial test case ok op@

To skip chunks without newly added lines. ok stsp@

Moves diff_chunk_type into the public diff API.

ok jamsek

Rather than skip lines, use the new diff APIs to directly seek to each chunk with newly added lines for more efficient conflict marker detection. ok stsp@

Contains new APIs for chunk offset retrieval.

Cover the case where a regular file would match if the ignore pattern did not have a trailing slash.

change got_img_commit_painting_request, got_imsg_tag_object and the data of GOT_IMSG_TRAVERSED_COMMITS not to copy the sha1 digest to the imsg buffer and then from it to a new struct got_object_id but send directly the whole struct. ok stsp@