The extra space before the colon looked uncanny. The rest is just code
indentation improvements.

Better diff with the --ignore-all-space --word-diff options.

There is room for further improvement in the dynamic between HPACK and
the HTTP/2 session, but this will serve as the first step.

Conflicts:
	include/tbl/h2_error.h

There are other components than the cache process that could benefit
from it, in particular libvcc. The relationship with vas.h is somewhat
unfortunate but that also centralize the Tcheck() logic in pdiff() and
doesn't actually require vas.h unless the macros are used, in which
case it's almost guaranteed that the calling code already included
vas.h in the first place.

The benefits should outweigh the drawbacks.

Conflicts:
	bin/varnishd/cache/cache.h
	bin/varnishtest/vtc_http.c

This way it can be used almost anywhere in the code base and out of tree,
not just in the cache process. The function was slightly polished after
prior discussions with phk and slink.

Conflicts:
	include/vas.h

Its first action ${string,repeat,<uint>,<string>} helps simplify many
unwieldy test cases that will hopefully be easier to edit from now on.

Conflicts:
	bin/varnishtest/tests/c00071.vtc
	bin/varnishtest/tests/r02219.vtc
	bin/varnishtest/vtc_main.c

Conflicts:
	bin/varnishtest/vtc.c

Instead of having a mere value, these would be able to compute a macro
expansion. We parse the contents inside the ${...} delimiters as a VAV,
but there can't be (yet?) nested curly {braces}, even quoted.

The first argument inside the delimiters is the macro name, and other
VAV arguments are treated as arguments to the macro's function.

For example ${foo,bar,baz} would call the a macro "foo"'s function with
arguments "bar" and "baz". Simple macros don't take arguments and work
as usual.

Conflicts:
	bin/varnishtest/vtc.c
	bin/varnishtest/vtc_main.c

The latter operates on a VSB, which is always what call sites are doing
anyway. It also takes the responsibility of ignoring unknown macros, in
preparation for more responsibilities that will also require the ability
to fail a test case.

Conflicts:
	bin/varnishtest/vtc_http.c

I kept a variable called "s" to cut noise from the diff.

Before the h2 frame dispatch we only need to check that coming from a
HEADERS frame the very next frame is a CONTINUATION, when the HPACK
block didn't fit in the former.

The CONTINUATION dispatch will then make the stream consistency check.

Conflicts:
	bin/varnishtest/tests/t02005.vtc

When a stream times out waiting for window credits, and all the other
streams are broke, declare the whole connection bankrupt.

Conflicts:
	bin/varnishd/http2/cache_http2.h

It replaces idle_send_timeout when the stream is waiting for window
credits before sending more DATA frames. The idle_send_timeout will
still apply to individual writes to the socket, but triggering it is
considered a failure condition (this was already the case).

The two loops are merged into a single one to better deal with the
lack of ordering guarantees of request vs connection stream control
flow window crediting.

Refs #2980

Conflicts:
	bin/varnishd/http2/cache_http2_proto.c
	bin/varnishd/http2/cache_http2_send.c

This parameter needs to be somewhat high because web browsers may for
example only credit streams for image resources just enough to parse
metadata like width and height of a picture in order to perform layout
computations and fetch resources more sensitive to latency before the
effective image payloads.

Conflicts:
	include/tbl/params.h

Conflicts:
	bin/varnishd/http2/cache_http2_send.c
	include/tbl/h2_error.h

The new meaning for h2->sess->t_idle is now the time since the last
complete frame, except before the first frame where it corresponds to
the creation of the session.

Conflicts:
	bin/varnishd/http2/cache_http2_proto.c

And after issuing or receiving a goaway, stop processing frames when
there are no streams left.

Initially submitted as part of listen sockets management.

Refs #3959

Conflicts:
	bin/varnishd/http2/cache_http2_proto.c

Conflicts:
	bin/varnishd/http2/cache_http2_send.c

Conflicts:
	bin/varnishd/http2/cache_http2.h
	bin/varnishd/http2/cache_http2_proto.c

Conflicts:
	bin/varnishd/http2/cache_http2_send.c

The 503 synth and 500 minimal response status codes are too misleading
in this context, where the failure is attributed to the client. Among
existing 4XX status codes, this is the closest if we stretch the timeout
definition to "didn't complete rapidly enough before the client went
away".

Conflicts:
	bin/varnishd/cache/cache_req_fsm.c

There is no minimal 500 response on this branch.

Since Python 3.12 unknown escape sequences trigger a warning.

The matching regular expression did not align with the substitution
regular expression.

Refs d2e526ce

A VCL failure on the client side transitions to vcl_synth, except
failures from vcl_synth that lead to minimal errors. The ESI transport
is not allowed to reply with minimal responses so this would lead to a
panic.

On top of that, the vcl_req_reset feature flag emulates `return (fail)`
statements when an HTTP/2 client disconnected, resulting in the same
panic scenario.

For sub-requests, we masquerade the fail transition as a deliver and
trade the illegal minimal response for the synthetic response.

Fixes #4022

Conflicts:
	bin/varnishd/cache/cache_req_fsm.c

Found by @Dridi

Conflicts:
	doc/changes.rst