wireproto: define and implement HTTP handshake to upgrade protocol
When clients connect to repositories over HTTP, they issue a request
to the well-known URL "?cmd=capabilities" to fetch the repository
capabilities. This is the handshake portion of the HTTP protocol.
This commit defines a mechanism to use that HTTP request to return
information about modern server features.
If a client sends an X-HgUpgrade-* header containing a list of
client-supported API names, the server responds with a response
containing information about available services. This includes
the normal capabilities string. So if the server doesn't support
any newer services, the client can easily fall back.
By advertising supported services from clients, server operators
can see and log what client support exists in the wild. This will
also help with debugging.
The response contains the base path to API services. We know there
are potential issues with the <repo>/api/ URL space conflicting with
hgwebdir and subrepos. By making the API URL dynamic from the
perspective of the client, the URL for APIs is not subject to backwards
compatibility concerns - at least as long as a ?cmd=capabilities request
is made.
We've also defined the ``cbor`` client capability for the X-HgProto-*
header. This MUST be sent in order to get the modern response from
"?cmd=capabilities". During implementation, I initially always sent
an application/mercurial-cbor response. However, the handshake
mechanism will be more future compatible if the client is in charge
of which formats to request. We already perform content negotiation
from X-HgProto-*, so keying off this for the capabilities response
feels appropriate.
In addition, I initially used application/cbor. However, it is
conceivable that a non-Mercurial server could serve application/cbor.
To rule out this possibility, I've invented a new media type that
is Mercurial specific and can't be confused for generic CBOR.
Differential Revision: https://phab.mercurial-scm.org/D3242
====================================
Testing head checking code: Case D-2
====================================
Mercurial checks for the introduction of new heads on push. Evolution comes
into play to detect if existing branches on the server are being replaced by
some of the new one we push.
This case is part of a series of tests checking this behavior.
Category D: remote head is "obs-affected" locally, but result is not part of the push
TestCase 1: remote branch has 2 changes, head is pruned, other is rewritten but result is not pushed
.. old-state:
..
.. * 1 changeset branch
..
.. new-state:
..
.. * old head is pruned
.. * 1 new branch succeeding to the other changeset in the old branch
.. * 1 new unrelated branch
..
.. expected-result:
..
.. * push allowed
.. * pushing only the unrelated branch: denied
..
.. graph-summary:
..
.. B ⊗
.. |
.. A ø⇠○ A'
.. |/
.. | ◔ C
.. |/
.. ●
$ . $TESTDIR/testlib/push-checkheads-util.sh
Test setup
----------
$ mkdir D2
$ cd D2
$ setuprepos
creating basic server and client repo
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd server
$ mkcommit B0
$ cd ../client
$ hg pull
pulling from $TESTTMP/D2/server
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets d73caddc5533
(run 'hg update' to get a working copy)
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mkcommit A1
created new head
$ hg debugobsolete `getid "desc(A0)" ` `getid "desc(A1)"`
obsoleted 1 changesets
1 new orphan changesets
$ hg debugobsolete --record-parents `getid "desc(B0)"`
obsoleted 1 changesets
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mkcommit C0
created new head
$ hg log -G --hidden
@ 0f88766e02d6 (draft): C0
|
| o f6082bc4ffef (draft): A1
|/
| x d73caddc5533 (draft): B0
| |
| x 8aaa48160adc (draft): A0
|/
o 1e4be0697311 (public): root
Actual testing
--------------
$ hg push --rev 'desc(C0)'
pushing to $TESTTMP/D2/server
searching for changes
abort: push creates new remote head 0f88766e02d6!
(merge or see 'hg help push' for details about pushing new heads)
[255]
$ cd ../..