got-notify-http: parse diffstat; adjust tag/commit

add test_tag_changed() for got-notify-http at the moment it is indistinguishable from the created tag.

got-notify-http: handle new tags

got-notify-http: handle branch removals

http_notification.sh: add a testcase add test_branch_created(). at the moment this is not different from a "normal" commit notification but it'll change in the future and it's handy to have it for an upcoming branch removed notification.

got-notify-http: add a type:commit field in the json will help to differentiate these notification objects from the others.

got-notify-http: change the layout of the json Split the author/committer in sub-fields, rename author -> committer in the short format parser and cache the author for the long format in case it's the same user as the committer. Put a copy of the first line of the commit message in the "short_message" field. There's some redundancy now, but it's to make consuming easier. ok stsp@

fix typo in a comment

got-notify-http: fix unicode handling JSON strings are made of UNICODE codepoints, of which only \, " and control characters have to be escaped, and the whole document MUST be encoded in UTF-8. The current code generates invalid strings for non-ASCII characters, so it has to be made UTF-8 aware. tedu' isu8cont() can't be used since it allows surrogate pairs and overlong sequences which will cause decoding errors on the receiving side. Similarly, mbtowc() depends on the current locale and could cause issues in -portable. Instead, bundle Björn Höhrmann's "Flexible and Economical UTF-8 Decoder" and use it to parse the text. Decoding errors results in the replacement character U+FFFD being emitted and the bytes considered so far to be discarded; the decoder is then restarted with the next byte. Git commit messages don't carry the notion of the encoding, but it's reasonable to expect UTF-8 (which is a superset of ASCII). For other more esotic encodings, the commit id can be used to manually extract the data. ok stsp@

http_notification regress: prettify the json long lines are not manegeable. split the json over multiple lines, then use ed to join everything back in a single one.

regress: http-server: hide the HTTP headers The http-server script is already validating the headers, doing so in the regress too is not helpful.

add got-notify-http ok stsp@