This replaces previous attempts to fix zodb/internal/weak with patches
from master.

* master:
  go/zodb/internal/weak: Disable support for weak references
  go/zodb/internal/weak: Assert that the object was not moved in the finalizer
  go/zodb/internal/weak: Try to fix GC crashes via reworking Ref to keep only one word instead of two

Experience shows that we cannot provide reliably working weak references
support without crashing GC because there needs to be a coordination in
between object resurrection and at least GC mark phase[1,2] with [3] and
[4] showing an idea what kind it coordination it needs to be.

And since support for weak references is upcoming in standard library
with hopefully Go 1.24 [5], it does not make sense to continue pushing
hard to make weak references work on our standalone side.

By disabling support for custom weak references we will avoid crashes,
but will start to leak unused objects in zodb.Connection live cache.
This should be relatively ok for now as WCFS in wendelin.core is
currently the only known ZODB/go user and it cares to drop ZBlk* state
after loading the data. The leak, thus, should be modest with,
hopefully, not creating problems in practice.

And once std package weak is out there we will switch to that restoring
automatic LiveCache cleanup.

[1] https://github.com/golang/go/issues/41303
[2] wendelin.core@9b44fc23
[3] https://github.com/golang/go/commit/dfc86e922cd0
[4] https://github.com/golang/go/commit/79fd633632cd
[5] https://github.com/golang/go/issues/67552

/reviewed-by @levin.zimmermann
/reviewed-on !11

This is good to do since we are relying on non-moving property of
current GC. It never triggered but it removed one uncertainty while
debugging GC crash issue. Good to have it in place.

/reviewed-by @levin.zimmermann
/reviewed-on !11

We are observing garbage-collector crashes due to weak package under
load(*) with GC crashing as e.g.

    runtime: full=0xc0001f10000005 next=205 jobs=204 nDataRoots=1 nBSSRoots=1 nSpanRoots=16 nStackRoots=184
    panic: non-empty mark queue after concurrent mark
    fatal error: panic on system stack

    runtime stack:
    runtime.throw({0x5c60fe?, 0x601d70?})
            /home/kirr/src/tools/go/go1.21/src/runtime/panic.go:1077 +0x5c fp=0xc000051e88 sp=0xc000051e58 pc=0x436efc
    panic({0x585100?, 0x601d70?})
            /home/kirr/src/tools/go/go1.21/src/runtime/panic.go:840 +0x6ea fp=0xc000051f38 sp=0xc000051e88 pc=0x436e0a
    runtime.gcMark(0x118946?)
            /home/kirr/src/tools/go/go1.21/src/runtime/mgc.go:1464 +0x40c fp=0xc000051fb0 sp=0xc000051f38 pc=0x41bd6c
    runtime.gcMarkTermination.func1()
            /home/kirr/src/tools/go/go1.21/src/runtime/mgc.go:962 +0x17 fp=0xc000051fc8 sp=0xc000051fb0 pc=0x41b277
    runtime.systemstack()
            /home/kirr/src/tools/go/go1.21/src/runtime/asm_amd64.s:509 +0x4a fp=0xc000051fd8 sp=0xc000051fc8 pc=0x468eea

One problem in current implementation is that weak.Ref keeps two words
for the copy of original interface object and recreates that interface
object on Ref.Get from those two words _nonatomically_. Which is
explicitly documented by Go memory model as something that can lead to
corrupted memory and crashes. From https://go.dev/ref/mem#restrictions:

    This means that races on multiword data structures can lead to
    inconsistent values not corresponding to a single write. When the values
    depend on the consistency of internal (pointer, length) or (pointer,
    type) pairs, as can be the case for interface values, maps, slices, and
    strings in most Go implementations, such races can in turn lead to
    arbitrary memory corruption.

We can avoid doing multiword writes during object resurrection by using
concrete type T* instead of interface{}.

Unfortunately as wendelin.core@9b44fc23
shows it does not help with the above issue and the GC continues to
crash with the same "panic: non-empty mark queue after concurrent mark"
message. This is because weak.Ref implementation needs tight integration
with concurrent GC that Go does and in practice we are unable to do that
from outside of Go runtime internals. See e.g.
https://github.com/golang/go/commit/dfc86e922cd0 and
https://github.com/golang/go/commit/79fd633632cd to get an idea what
kind of integration that needs to be.

Anyway before disabling weak references support I wanted to commit this
change to show that one-word approach was tried and it does not work.
This leaves a trace in the history.

On the good side we are going to use standard package weak in the future
hopefully (https://github.com/golang/go/issues/67552). That needs to
wait for at least Go 1.24 though.

(*) see https://github.com/golang/go/issues/41303 for details

/reviewed-by @levin.zimmermann
/reviewed-on !11

* master:
  go/neo/proto: Update 'Compression' to int to support different compression algorithms

With nexedi/neoppod@fd80cc30 NEO/py added support to encode the compression
algorithm with the 'Compression' parameter. Before this, compression could
only be true (= with compression) or false (= without compression). Now
the absence of compression is encoded with 0. Any other number than 0
encodes a compression algorithm. The mapping is currently:

	1 = zlib

In the future, 2 could mean zstd [1].

[1] https://github.com/facebook/zstd/issues/1134

/reviewed-by @kirr
/reviewed-on !6

With nexedi/neoppod@fd80cc30 NEO/py added support to encode the compression
algorithm with the 'Compression' parameter. Before this, compression could
only be true (= with compression) or false (= without compression). Now
the absence of compression is encoded with 0. Any other number than 0
encodes a compression algorithm. The mapping is currently:

	1 = zlib

In the future, 2 could mean zstd [1].

[1] https://github.com/facebook/zstd/issues/1134

/reviewed-by @kirr
/reviewed-on !6

When a node tries to connect to another node it initially sends a
'RequestIdentification' packet. The other node can either reply with
'AcceptIdentification' or in case of a secondary master with
'NotPrimaryMaster'.

In the second case the message id differs from the initial requests
message id. This makes it difficult in a multi-threaded implementation
to proceed this answer: due to the different msg/connection - id the
multi-threaded implementation tries to proceed this incoming message in
a different thread, while the requesting thread waits forever for its
peers reply.

The most straightforward solution is to use the same connection - id for
both possible answers to the 'RequestIdentification' packet. This
doesn't break given NEO/py implementation and is only a small patch.
A workaround in a multi-threaded implementation on the other hand
seems to be much more complicated and time-consuming. Finally it also makes
sense semantically, because "Message IDs are used to identify response
packets" and in the given context the 'NotPrimaryMaster' *is* the de facto
response of a 'RequestIdentification'.

/suggested-at !2
/proposed-for-review-at nexedi/neoppod!20

* master:
  go/neo/proto: Fix KnownMasterList nesting
  go/neo/proto/RowInfo: Fix representation on the wire

Before this patch, the 'KnownMasterList' field of the 'NotPrimaryMaster'
was expected to be structured in the following way:

	ArrayHeader (KnownMasterList)

	    ArrayHeader (KnownMaster)

		ArrayHeader (Address)

		    Host (string)
		    Port (uint16)

However NEO/py sends the following structure:

	ArrayHeader (KnownMasterList)

	    ArrayHeader (Address)

		Host (string)
		Port (uint16)

This also makes sense, as 'KnownMaster' doesn't need to add another
nesting, because it only includes the address.

This patch amends the NEO/go protocol definition to transparently
represent the nesting as it's send by NEO/py. See also
levin.zimmermann/neoppod@18287612 for a similar issue.

----
kirr: tests currently live only on t branch.

/reviewed-by @kirr
/reviewed-on !6

Some NEO protocol packets have the field 'RowList'. This field contains
information about each row of a partition table. In NEO/go the information
of each row is represented with the 'RowInfo' type [1]. This type is defined
as a struct with the field ‘CellList’. ‘CellList’ is defined as a list of
'CellInfo' [1] (e.g. an entry for each cell).

NEO/go {en,de}codes struct types with ‘genStructHead’ (structures in
golang are encoded as arrays in msgpack) [2]. From the 'RowList'
definition, the msgpack decoder currently expects the following msgpack
array structure:

    ArrayHeader (RowList)

        ArrayHeader (RowInfo)

            ArrayHeader (CellList)

                ArrayHeader (CellInfo)

                    int32 (NID)
                    enum (State)

However NEO/py actually sends:

    ArrayHeader (RowList)

        ArrayHeader (CellList)

            ArrayHeader (CellInfo)

                int32 (NID)
                enum (State)

In other words, currently the NEO/go msgpack encoder expects one more
nesting, which NEO/py doesn’t provide (and which also doesn’t seem to
be necessary as the outer nesting would always only contain one
element). We could adjust the msgpack {en,de}coder to introduce an
exception for the 'RowInfo' type, however as the protocol definition in
'proto.go' aims to transparently reflect the structure of the packets on
the wire, it seems to be more appropriate to fix this straight in the
protocol definition. This is also less error-prone as we don't have to
fix all the different positions of the encoder, decoder & sizer and it's
less code (particularly if 'RowInfo' doesn't stay the only case for such
an issue).

[1] https://lab.nexedi.com/kirr/neo/-/blob/1ad088c8/go/neo/proto/proto.go#L391-394
[2] https://lab.nexedi.com/kirr/neo/-/blob/1ad088c8/go/neo/proto/protogen.go#L1770-1775

--------

kirr: I've applied the following interdiff to the original patch of
levin.zimmermann/neoppod@c93d5dbc :

    --- a/go/neo/neo_test.go
    +++ b/go/neo/neo_test.go
    @@ -100,7 +100,7 @@ func _TestMasterStorage(t0 *tEnv) {
                    PTid:           1,
                    NumReplicas:    0,
                    RowList:        []proto.RowInfo{
    -                       proto.RowInfo{proto.CellInfo{proto.NID(proto.STORAGE, 1), proto.UP_TO_DATE}},
    +                       {proto.CellInfo{proto.NID(proto.STORAGE, 1), proto.UP_TO_DATE}},
                    },
            }))

    @@ -173,7 +173,7 @@ func _TestMasterStorage(t0 *tEnv) {
                    PTid:           1,
                    NumReplicas:    0,
                    RowList:        []proto.RowInfo{
    -                       proto.RowInfo{proto.CellInfo{proto.NID(proto.STORAGE, 1), proto.UP_TO_DATE}},
    +                       {proto.CellInfo{proto.NID(proto.STORAGE, 1), proto.UP_TO_DATE}},
                    },
            }))

    --- a/go/neo/proto/proto_test.go
    +++ b/go/neo/proto/proto_test.go
    @@ -210,9 +210,9 @@ func TestMsgMarshal(t *testing.T) {
                            PTid:        0x0102030405060708,
                            NumReplicas: 34,
                            RowList: []RowInfo{
    -                               {CellInfo{11, UP_TO_DATE}, CellInfo{17, OUT_OF_DATE}},
    -                               {CellInfo{11, FEEDING}},
    -                               {CellInfo{11, CORRUPTED}, CellInfo{15, DISCARDED}, CellInfo{23, UP_TO_DATE}},
    +                               {{11, UP_TO_DATE}, {17, OUT_OF_DATE}},
    +                               {{11, FEEDING}},
    +                               {{11, CORRUPTED}, {15, DISCARDED}, {23, UP_TO_DATE}},
                            },
                            },

    @@ -229,9 +229,9 @@ func TestMsgMarshal(t *testing.T) {
                            hex("cf0102030405060708") +
                            hex("22") +
                            hex("93") +
    -                               hex("92"+"920bd40001"+"9211d40000") +
    -                               hex("91"+"920bd40002") +
    -                               hex("93"+"920bd40003"+"920fd40004"+"9217d40001"),
    +                               hex("92"+"920bd40401"+"9211d40400") +
    +                               hex("91"+"920bd40402") +
    +                               hex("93"+"920bd40403"+"920fd40404"+"9217d40401"),
                    },

                    // map[Oid]struct {Tid,Tid,bool}

for cosmetics and because the tests were failing as

    --- FAIL: TestMsgMarshal (0.00s)
        proto_test.go:106: M/proto.AnswerPartitionTable: encode result unexpected:
        proto_test.go:107:  have: 93cf0102030405060708229392920bd404019211d4040091920bd4040293920bd40403920fd404049217d40401
        proto_test.go:108:  want: 93cf0102030405060708229392920bd400019211d4000091920bd4000293920bd40003920fd400049217d40001

/reviewed-by @kirr
/reviewed-on !6

Before this patch, the 'KnownMasterList' field of the 'NotPrimaryMaster'
was expected to be structured in the following way:

	ArrayHeader (KnownMasterList)

	    ArrayHeader (KnownMaster)

		ArrayHeader (Address)

		    Host (string)
		    Port (uint16)

However NEO/py sends the following structure:

	ArrayHeader (KnownMasterList)

	    ArrayHeader (Address)

		Host (string)
		Port (uint16)

This also makes sense, as 'KnownMaster' doesn't need to add another
nesting, because it only includes the address.

This patch amends the NEO/go protocol definition to transparently
represent the nesting as it's send by NEO/py. See also
levin.zimmermann/neoppod@18287612 for a similar issue.

/reviewed-by @kirr
/reviewed-on !6

Some NEO protocol packets have the field 'RowList'. This field contains
information about each row of a partition table. In NEO/go the information
of each row is represented with the 'RowInfo' type [1]. This type is defined
as a struct with the field ‘CellList’. ‘CellList’ is defined as a list of
'CellInfo' [1] (e.g. an entry for each cell).

NEO/go {en,de}codes struct types with ‘genStructHead’ (structures in
golang are encoded as arrays in msgpack) [2]. From the 'RowList'
definition, the msgpack decoder currently expects the following msgpack
array structure:

    ArrayHeader (RowList)

        ArrayHeader (RowInfo)

            ArrayHeader (CellList)

                ArrayHeader (CellInfo)

                    int32 (NID)
                    enum (State)

However NEO/py actually sends:

    ArrayHeader (RowList)

        ArrayHeader (CellList)

            ArrayHeader (CellInfo)

                int32 (NID)
                enum (State)

In other words, currently the NEO/go msgpack encoder expects one more
nesting, which NEO/py doesn’t provide (and which also doesn’t seem to
be necessary as the outer nesting would always only contain one
element). We could adjust the msgpack {en,de}coder to introduce an
exception for the 'RowInfo' type, however as the protocol definition in
'proto.go' aims to transparently reflect the structure of the packets on
the wire, it seems to be more appropriate to fix this straight in the
protocol definition. This is also less error-prone as we don't have to
fix all the different positions of the encoder, decoder & sizer and it's
less code (particularly if 'RowInfo' doesn't stay the only case for such
an issue).

[1] https://lab.nexedi.com/kirr/neo/-/blob/1ad088c8/go/neo/proto/proto.go#L391-394
[2] https://lab.nexedi.com/kirr/neo/-/blob/1ad088c8/go/neo/proto/protogen.go#L1770-1775

--------

kirr: I've applied the following interdiff to the original patch of
levin.zimmermann/neoppod@c93d5dbc :

    --- a/go/neo/neo_test.go
    +++ b/go/neo/neo_test.go
    @@ -100,7 +100,7 @@ func _TestMasterStorage(t0 *tEnv) {
                    PTid:           1,
                    NumReplicas:    0,
                    RowList:        []proto.RowInfo{
    -                       proto.RowInfo{proto.CellInfo{proto.NID(proto.STORAGE, 1), proto.UP_TO_DATE}},
    +                       {proto.CellInfo{proto.NID(proto.STORAGE, 1), proto.UP_TO_DATE}},
                    },
            }))

    @@ -173,7 +173,7 @@ func _TestMasterStorage(t0 *tEnv) {
                    PTid:           1,
                    NumReplicas:    0,
                    RowList:        []proto.RowInfo{
    -                       proto.RowInfo{proto.CellInfo{proto.NID(proto.STORAGE, 1), proto.UP_TO_DATE}},
    +                       {proto.CellInfo{proto.NID(proto.STORAGE, 1), proto.UP_TO_DATE}},
                    },
            }))

    --- a/go/neo/proto/proto_test.go
    +++ b/go/neo/proto/proto_test.go
    @@ -210,9 +210,9 @@ func TestMsgMarshal(t *testing.T) {
                            PTid:        0x0102030405060708,
                            NumReplicas: 34,
                            RowList: []RowInfo{
    -                               {CellInfo{11, UP_TO_DATE}, CellInfo{17, OUT_OF_DATE}},
    -                               {CellInfo{11, FEEDING}},
    -                               {CellInfo{11, CORRUPTED}, CellInfo{15, DISCARDED}, CellInfo{23, UP_TO_DATE}},
    +                               {{11, UP_TO_DATE}, {17, OUT_OF_DATE}},
    +                               {{11, FEEDING}},
    +                               {{11, CORRUPTED}, {15, DISCARDED}, {23, UP_TO_DATE}},
                            },
                            },

    @@ -229,9 +229,9 @@ func TestMsgMarshal(t *testing.T) {
                            hex("cf0102030405060708") +
                            hex("22") +
                            hex("93") +
    -                               hex("92"+"920bd40001"+"9211d40000") +
    -                               hex("91"+"920bd40002") +
    -                               hex("93"+"920bd40003"+"920fd40004"+"9217d40001"),
    +                               hex("92"+"920bd40401"+"9211d40400") +
    +                               hex("91"+"920bd40402") +
    +                               hex("93"+"920bd40403"+"920fd40404"+"9217d40401"),
                    },

                    // map[Oid]struct {Tid,Tid,bool}

for cosmetics and because the tests were failing as

    --- FAIL: TestMsgMarshal (0.00s)
        proto_test.go:106: M/proto.AnswerPartitionTable: encode result unexpected:
        proto_test.go:107:  have: 93cf0102030405060708229392920bd404019211d4040091920bd4040293920bd40403920fd404049217d40401
        proto_test.go:108:  want: 93cf0102030405060708229392920bd400019211d4000091920bd4000293920bd40003920fd400049217d40001

/reviewed-by @kirr
/reviewed-on !6

* master:
  go/neo/neonet: DialLink: Fix SIGSEGV in case client handshake fails
  go/neo/neonet: Demonstrate DialLink misbehaviour when all handshake attempts fail

In case the last 'handshakeClient' call returns an error, 'DialLink'
returns 'link = nil, err = nil'. Callers of 'DialLink' then don't
recognize that 'link' is 'nil', as it's the convention to only check if
'err' is 'nil', which leads to a 'segmentation violation' as soon as
subsequent code tries to access fields of 'link':

```
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x14 pc=0x7087ae]

goroutine 5 [running]:
lab.nexedi.com/kirr/neo/go/neo/neonet.(*NodeLink).NewConn(0x0)
	/srv/slapgrid/slappart82/srv/runner/instance/slappart6/software_release/parts/wendelin.core/wcfs/neo/go/neo/neonet/connection.go:404 +0x4e
lab.nexedi.com/kirr/neo/go/neo/xneo.Dial.func1()
	/srv/slapgrid/slappart82/srv/runner/instance/slappart6/software_release/parts/wendelin.core/wcfs/neo/go/neo/xneo/connect.go:138 +0x52
lab.nexedi.com/kirr/neo/go/internal/xio.WithCloseOnErrCancel.func2()
	/srv/slapgrid/slappart82/srv/runner/instance/slappart6/software_release/parts/wendelin.core/wcfs/neo/go/internal/xio/xio.go:114 +0x6a
created by lab.nexedi.com/kirr/neo/go/internal/xio.WithCloseOnErrCancel in goroutine 21
	/srv/slapgrid/slappart82/srv/runner/instance/slappart6/software_release/parts/wendelin.core/wcfs/neo/go/internal/xio/xio.go:109 +0x1ad
```

This patch fixes this issue so that now 'err' and 'link' are never both
'nil' again.

/reviewed-by @kirr
/reviewed-on !10

Levin found that when all handshake attempts fail DialLink returns
both link=nil and err=nil which breaks what callers expect and lead to
segmentation fault when accessing that nil link.

-> Add test to demonstrate the problem.

With xfail removed that test currently fails as

    --- FAIL: TestDialLink_AllHandshakeErr (0.00s)
    panic: lab.nexedi.com/kirr/neo/go/neo/neonet.TestDialLink_AllHandshakeErr.gox.func4.1: lab.nexedi.com/kirr/neo/go/neo/neonet.TestDialLink_AllHandshakeErr.func2: DialLink to handshake-rejecting server:
    have: link=<nil> err=<nil>
    want: link=<nil> err=client:1 - server:2: handshake (client): unexpected EOF [recovered]

We will fix the problem in the next patch.

/reported-by @levin.zimmermann
/reported-at !10

I realized a minor mistake I did in writing the tests that needs to
be fixed in order to have reliable test results.

/reviewed-by @kirr
/reviewed-on kirr/neo!9

During our work on 'wendelin.core' URI normalization, Kirill Smelkov
noted a inconsistency between NEO/py and NEO/go URI parser [1]: NEO/py
drops empty query options, while NEO/go preserves them. Let's fix this
inconsistency by adjusting NEO/go to NEO/py behaviour.

[1] nexedi/wendelin.core!28 (comment 212447)

/reviewed-by @kirr
/reviewed-on kirr/neo!9

Hello Kirill,

in nexedi/neoppod!18 and nexedi/neoppod!21 we could find a common solution for a zurl format that previously diverged between NEOgo and NEOpy. The purpose of this MR is to sync again NEOgo and NEOpy zurl format. After merging this, we can continue to sync NEO zurl format in 'wendelin.core' & 'slapos'. Then we finally have unified approach again, which simplifies understanding and reduces unnecessary mental overhead.

As this is strongly related to nexedi/neoppod!21 I thought it'd be a good idea to generally reduce difference and to replace WIP commits with merged NEOpy upstream commits.

Best, Levin

/reviewed-by @kirr
/reviewed-on !7

* lev/sync-zurl:
  client: Don't allow oPtion_nAme in zurl
  app: Remember SSL credentials so that it is possible to retrieve them
  client: Allow to force TLS via neos:// scheme
  client: Don't allow master_nodes and name to be present in options
  Revert "."
  Revert "Y client: Fix URI scheme to move credentials out of query"
  Revert "X Adjust NEO/go to neo:// URL change + py fixups"
  Revert "fixup! Y client: Fix URI scheme to move credentials out of query"
  Revert "Y client: Don't allow master_nodes and name to be present in options"
  go/client/zurl: Sync format to py upstream

Julien notes this is very likely unneeded:
nexedi/neoppod!21 (diffs, comment 195929)

We had it like this since 01a01c8c (client: Add support for zodburi),
but I rechecked zodburi codebase now and it does not do any similar
lowering anywhere.

So drop support for case normalization in zurl options.

/cc @levin.zimmermann
/reviewed-by @jm
/reviewed-on nexedi/neoppod!21

(cherry-picked from commit 798c9f25)

Unfortunately after creating SSL context it is not possible, or at least
I could not find how, to retrieve original credentials with which the
context was created. However wendelin.core needs to be able to take a
client storage, reconstruct zurl to refer to that particular storage,
and pass that zurl to wcfs, so that wcfs, in turn, could access the same
ZODB database.

Given a NEO client instance, it is already possible to retrieve
master_nodes, cluster name, and detect whether SSL is being in use.
However without being able to retrieve original SSL credentials,
reconstructed zurl will not be full and wcfs won't be able to use
exactly the same secrets as python part does.

-> Help wendelin.core by remembering which ca/cert/key were used to
build SSL context.

This information is used by zstor_2zurl in wendelin.core here:

https://lab.nexedi.com/nexedi/wendelin.core/blob/885b3556/lib/zodb.py#L390-418

/cc @levin.zimmermann
/reviewed-by @jm
/reviewed-on nexedi/neoppod!21

Similarly to how it is done with e.g. http:// and https:// - if neos://
is given TLS usage is forced and ca/cert/key must be there either in the
URI itself, or in $NEO_CA, $NEO_CERT and $NEO_KEY environment variables
mimicking the way how e.g. for https:// TLS credentials are taken from
host environment, not from the uri.

The latter might be usability convenience, but is also useful for WCFS
which needs to be able to remove secrets from uri on zurl normalization.

Please see discussion at nexedi/neoppod!18 (comment 184439)
for details.

/cc @levin.zimmermann
/reviewed-by @jm
/reviewed-on nexedi/neoppod!21

(cherry-picked from commit bc3e38ea)

Because list of masters and cluster name must be already present in
netloc and path. Previously e.g.

	neo://db@α,β,γ?master_nodes=a,b,c"

would mean to use master nodes {a,b,c} not {α,β,γ}. Now it is treated as
invalid URI to remove ambiguity. Same for cluster name.

/cc @levin.zimmermann
/reviewed-by @jm
/reviewed-on nexedi/neoppod!21

(cherry-picked from commit 22ccebd6)

This reverts commit a2f192cb. This has
been merged upstream with nexedi/neoppod@17af7f27.
We should rather cherry-pick upstream commit.

This reverts commit b9a42957. In
nexedi/neoppod!18 and
nexedi/neoppod!21 a common
solution for a zurl format was found. This common format keeps
credentials in the query, therefore we should revert patch
b9a42957.

This reverts the py part of kirr/neo@8c974485.
go parts of this patch are handled in 70c0a984.

This reverts commit cf685fb5. This used
to be a divergence between NEO/py and NEO/go, however in nexedi/neoppod!18 and
nexedi/neoppod!21 a common
solution for a zurl format was found. This common format keeps
credentials in the query, therefore we should revert patch
cf685fb5.

This reverts commit 6047f893 in order to
replace it with py upstream commit nexedi/neoppod@22ccebd6.

NEO/go and NEO/py zurl format diverged over time:

- kirr/neo@8c974485

However with nexedi/neoppod!21 a
common solution was found. From there, this patch aims to adjust NEO/go zurl
format to be in sync with NEO/py zurl format again.

* master:
  go/zodb: Handle common options in zurl in generic layer

/reviewed-by @kirr
/reviewed-on kirr/neo!4

* kirr/t+new-uri:
  Revert "Y client: Adjust URI scheme to move client-specific options to fragment"
  fixup! client.go: Fix URI client option parsing for supported + unsupported options
  client.go: Fix URI client option parsing for supported + unsupported options
  fixup! client_test: Add tests for NEO URI parser
  client_test: Add tests for NEO URI parser
  fixup! client: Refactor openClientByURL for easier testing
  client: Refactor openClientByURL for easier testing
  Y go/zodb: Handle common options in zurl in generic layer

Offload drivers from handling options such as ?read-only=1 and force
them to deal with such options only via DriverOptions, never zurl.

See added comment for details.

/reviewed-by @levin.zimmermann
/reviewed-on kirr/neo!4

This reverts commit kirr/neo@4c9414ea.
This patch was added at a time when nexedi/neoppod!18 wasn't
resolved yet, but we already wanted to proceed with WCFS. Now the NEO MR
is resolved and we decided to mostly leave the NEO zurl as it was
originally implemented in nexedi/neoppod!6.
This means we don't need this patch anymore which changed the NEO
zurl format.

readonly is handled by common zodb.OpenDriver.

Before this patch, the parser ignored options which were already supported
by the client (for instance 'read-only') and even raised an error. But the
client can already use this option: as a9246333 describes this should happen in the
local storage URL parser.

Furthermore not-yet-supported client options (for instance compress) broke
the NEO client before this patch. Now these options only raise a warning which
informs the user that they are ignored. Why? We want to use pre-complete NEO
in real-world projects together with NEO/py clusters. Those real-world projects
may already specify options which aren't supported by our NEO/go client yet.
But it doesn't matters so much, because those options are mostly
relevant for other NEO/py cluster clients (e.g. zope nodes). Instead of
filtering those parameters before parsing them to NEO/go in a higher
level (e.g. SlapOS), NEO/go should already support any valid NEO URL
and raise warnings for not yet implemented features.

- use simplified parseURL signature - DriverOptions are not passed nor changed there.
- read-only is handled by generic zodb layer not neo.parseURL .

This test was missing so far. Particularly recent changes of the
NEO URI scheme [1], but also problems with valid old URI [2] stressed
out the necessity for comprehensive NEO URI parser tests.

[1] kirr/neo@4c9414ea
[2] 573514c6 (comment 184417)

- no need to pass DriverOptions into parseURL - it is only zurl that is
  parsed, and also DriverOptions should not be changed by the opener.

- no need to document "If anything fails within this process an error
  and nil are returned." because that is standard omnipresent Go convention.

With all the recent changes of the NEO URI scheme we need to reliably test
the function which parses the URI and convert it into the different
parameter. Testing is much simpler if we can only analyse how the URI
parsing works. Therefore this patch moves NEO URI parsing to an
external function.

Offload drivers from handling options such as ?read-only=1 and force
them to deal with such options only via DriverOptions, never zurl.

See added commend for details.