Suggested by Ricardo Wurmus <rekado@elephly.net>.
* guix/channels.scm (<channel-news-entry>)[tag]: New field.
(sexp->channel-news-entry): Accept either 'commit' or 'tag' in 'entry'
forms.
(resolve-channel-news-entry-tag): New procedure.
(channel-news-for-commit): Move 'with-repository' form one level
higher. Call 'resolve-channel-news-entry-tag' on all the news entries.
* guix/tests/git.scm (populate-git-repository): Add clause for 'tag'.
* tests/channels.scm ("channel-news, one entry"): Create a tag and add
an entry with a tag. Check that the tag is resolved and also visible in
the <channel-news-entry> record.
* doc/guix.texi (Channels): Mention tags in news entries.
* guix/channels.scm (<channel-metadata>)[news-file]: New field.
(read-channel-metadata): Set the 'news-file' field.
(read-channel-metadata-from-source): Likewise.
(<channel-news>, <channel-news-entry>): New record types.
(sexp->channel-news-entry, read-channel-news)
(channel-news-for-commit): New procedures.
* guix/tests/git.scm (populate-git-repository): For 'add', allow
CONTENTS to be a procedure.
* tests/channels.scm ("channel-news, no news")
("channel-news, one entry"): New tests.
* doc/guix.texi (Channels): Document it.
* guix/tests/http.scm (call-with-http-server): Replace 'code' and 'data'
parameters with 'responses+data'. Compute RESPONSES as a function of
that. Remove #:headers parameter.
[http-write]: Quit only when RESPONSES is empty.
[server-body]: Get the response and data from RESPONSES, and set it to
point to the rest.
(with-http-server): Adjust accordingly.
* tests/derivations.scm ("'download' built-in builder")
("'download' built-in builder, invalid hash")
("'download' built-in builder, not found")
("'download' built-in builder, check mode"): Adjust to new
'with-http-server' interface.
* tests/lint.scm ("home-page: 200")
("home-page: 200 but short length")
("home-page: 404", "home-page: 301, invalid"):
("home-page: 301 -> 200", "home-page: 301 -> 404")
("source: 200", "source: 200 but short length")
("source: 404", "source: 404 and 200")
("source: 301 -> 200", "source: 301 -> 404"):
("github-url", github-url): Likewise.
* tests/swh.scm (with-json-result)
("lookup-origin, not found"): Likewise.
* tests/lint.scm (%http-server-port, %local-url)
(%http-server-socket, http-write, %http-server-lock)
(%http-server-ready, http-open, stub-http-server)
(call-with-http-server, with-http-server): Move to (guix tests http).
Adjust tests for %HTTP-SERVER-SOCKET as a promise and %LOCAL-URL as a
parameter.
* guix/tests/http.scm: New file.
* Makefile.am (dist_noinst_DATA): Add it.
(GOBJECTS): Add .go files for all of $(dist_noinst_DATA).
(make-go): Depend on $(dist_noinst_DATA).