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
#testcases flat tree
$ . "$TESTDIR/narrow-library.sh"
#if tree
$ cat << EOF >> $HGRCPATH
> [experimental]
> treemanifest = 1
> EOF
#endif
create full repo
$ hg init master
$ cd master
$ cat >> .hg/hgrc <<EOF
> [narrow]
> serveellipses=True
> EOF
$ mkdir inside
$ echo inside > inside/f1
$ mkdir outside
$ echo outside > outside/f1
$ hg ci -Aqm 'initial'
$ echo modified > inside/f1
$ hg ci -qm 'modify inside'
$ hg co -q 0
$ echo modified > outside/f1
$ hg ci -qm 'modify outside'
$ echo modified again >> outside/f1
$ hg ci -qm 'modify outside again'
$ cd ..
$ hg clone --narrow ssh://user@dummy/master narrow --include inside
requesting all changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 2 changes to 1 files (+1 heads)
new changesets *:* (glob)
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd narrow
$ cat >> $HGRCPATH <<EOF
> [extensions]
> strip=
> EOF
Can strip and recover changesets affecting only files within narrow spec
$ hg co -r 'desc("modify inside")'
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm -f .hg/strip-backup/*-backup.hg
$ hg strip .
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-backup.hg (glob)
$ hg unbundle .hg/strip-backup/*-backup.hg
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets * (glob)
(run 'hg heads' to see heads, 'hg merge' to merge)
Can strip and recover changesets affecting files outside of narrow spec
$ hg co -r 'desc("modify outside")'
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg log -G -T '{rev} {desc}\n'
o 2 modify inside
|
| @ 1 modify outside again
|/
o 0 initial
$ hg debugdata -m 1
inside/f1\x004d6a634d5ba06331a60c29ee0db8412490a54fcd (esc) (flat !)
outside/f1\x0084ba604d54dee1f13310ce3d4ac2e8a36636691a (esc) (flat !)
inside\x006a8bc41df94075d501f9740587a0c0e13c170dc5t (esc) (tree !)
outside\x00255c2627ebdd3c7dcaa6945246f9b9f02bd45a09t (esc) (tree !)
$ rm -f .hg/strip-backup/*-backup.hg
$ hg strip .
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-backup.hg (glob)
$ hg unbundle .hg/strip-backup/*-backup.hg
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
new changesets * (glob)
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg log -G -T '{rev} {desc}\n'
o 2 modify outside again
|
| o 1 modify inside
|/
@ 0 initial
Check that hash of file outside narrow spec got restored
$ hg debugdata -m 2
inside/f1\x004d6a634d5ba06331a60c29ee0db8412490a54fcd (esc) (flat !)
outside/f1\x0084ba604d54dee1f13310ce3d4ac2e8a36636691a (esc) (flat !)
inside\x006a8bc41df94075d501f9740587a0c0e13c170dc5t (esc) (tree !)
outside\x00255c2627ebdd3c7dcaa6945246f9b9f02bd45a09t (esc) (tree !)
Also verify we can apply the bundle with 'hg pull':
$ hg co -r 'desc("modify inside")'
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm .hg/strip-backup/*-backup.hg
$ hg strip .
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-backup.hg (glob)
#if repobundlerepo
$ hg pull .hg/strip-backup/*-backup.hg
pulling from .hg/strip-backup/*-backup.hg (glob)
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets * (glob)
(run 'hg heads' to see heads, 'hg merge' to merge)
$ rm .hg/strip-backup/*-backup.hg
$ hg strip 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-backup.hg (glob)
$ hg incoming .hg/strip-backup/*-backup.hg
comparing with .hg/strip-backup/*-backup.hg (glob)
changeset: 0:* (glob)
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: initial
changeset: 1:9e48d953700d (flat !)
changeset: 1:3888164bccf0 (tree !)
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: modify outside again
changeset: 2:f505d5e96aa8 (flat !)
changeset: 2:40b66f95a209 (tree !)
tag: tip
parent: 0:a99f4d53924d (flat !)
parent: 0:c2a5fabcca3c (tree !)
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: modify inside
$ hg pull .hg/strip-backup/*-backup.hg
pulling from .hg/strip-backup/*-backup.hg (glob)
requesting all changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 2 changes to 1 files (+1 heads)
new changesets *:* (glob)
(run 'hg heads' to see heads, 'hg merge' to merge)
#endif