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sshpeer: initial definition and implementation of new SSH protocol...
sshpeer: initial definition and implementation of new SSH protocol The existing SSH protocol has several design flaws. Future commits will elaborate on these flaws as new features are introduced to combat these flaws. For now, hopefully you can take me for my word that a ground up rewrite of the SSH protocol is needed. This commit lays the foundation for a new SSH protocol by defining a mechanism to upgrade the SSH transport channel away from the default (version 1) protocol to something modern (which we'll call "version 2" for now). This upgrade process is detailed in the internals documentation for the wire protocol. The gist of it is the client sends a request line preceding the "hello" command/line which basically says "I'm requesting an upgrade: here's what I support." If the server recognizes that line, it processes the upgrade request and the transport channel is switched to use the new version of the protocol. If not, it sends an empty response, which is how all Mercurial SSH servers from the beginning of time reacted to unknown commands. The upgrade request is effectively ignored and the client continues to use the existing version of the protocol as if nothing happened. The new version of the SSH protocol is completely identical to version 1 aside from the upgrade dance and the bytes that follow. The immediate bytes that follow the protocol switch are defined to be a length framed "capabilities: " line containing the remote's advertised capabilities. In reality, this looks very similar to what the "hello" response would look like. But it will evolve quickly. The methodology by which the protocol will evolve is important. I'm not going to introduce the new protocol all at once. That would likely lead to endless bike shedding and forward progress would stall. Instead, I intend to tricle out new features and diversions from the existing protocol in small, incremental changes. To support the gradual evolution of the protocol, the on-the-wire advertised protocol name contains an "exp" to denote "experimental" and a 4 digit field to capture the sub-version of the protocol. Whenever we make a BC change to the wire protocol, we can increment this version and lock out all older clients because it will appear as a completely different protocol version. This means we can incur as many breaking changes as we want. We don't have to commit to supporting any one feature or idea for a long period of time. We can even evolve the handshake mechanism, because that is defined as being an implementation detail of the negotiated protocol version! Hopefully this lowers the barrier to accepting changes to the protocol and for experimenting with "radical" ideas during its development. In core, sshpeer received most of the attention. We haven't even implemented the server bits for the new protocol in core yet. Instead, we add very primitive support to our test server, mainly just to exercise the added code paths in sshpeer. Differential Revision: https://phab.mercurial-scm.org/D2061 # no-check-commit because of required foo_bar naming

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r35722:41ef02ba default
r35994:48a3a928 default
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test-merge7.t
151 lines | 4.2 KiB | text/troff | Tads3Lexer
initial
$ hg init test-a
$ cd test-a
$ cat >test.txt <<"EOF"
> 1
> 2
> 3
> EOF
$ hg add test.txt
$ hg commit -m "Initial"
clone
$ cd ..
$ hg clone test-a test-b
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
change test-a
$ cd test-a
$ cat >test.txt <<"EOF"
> one
> two
> three
> EOF
$ hg commit -m "Numbers as words"
change test-b
$ cd ../test-b
$ cat >test.txt <<"EOF"
> 1
> 2.5
> 3
> EOF
$ hg commit -m "2 -> 2.5"
now pull and merge from test-a
$ hg pull ../test-a
pulling from ../test-a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 96b70246a118
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg merge
merging test.txt
warning: conflicts while merging test.txt! (edit, then use 'hg resolve --mark')
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
[1]
resolve conflict
$ cat >test.txt <<"EOF"
> one
> two-point-five
> three
> EOF
$ rm -f *.orig
$ hg resolve -m test.txt
(no more unresolved files)
$ hg commit -m "Merge 1"
change test-a again
$ cd ../test-a
$ cat >test.txt <<"EOF"
> one
> two-point-one
> three
> EOF
$ hg commit -m "two -> two-point-one"
pull and merge from test-a again
$ cd ../test-b
$ hg pull ../test-a
pulling from ../test-a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 40d11a4173a8
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg merge --debug
searching for copies back to rev 1
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 96b70246a118, local: 50c3a7e29886+, remote: 40d11a4173a8
preserving test.txt for resolve of test.txt
starting 4 threads for background file closing (?)
test.txt: versions differ -> m (premerge)
picked tool ':merge' for test.txt (binary False symlink False changedelete False)
merging test.txt
my test.txt@50c3a7e29886+ other test.txt@40d11a4173a8 ancestor test.txt@96b70246a118
test.txt: versions differ -> m (merge)
picked tool ':merge' for test.txt (binary False symlink False changedelete False)
my test.txt@50c3a7e29886+ other test.txt@40d11a4173a8 ancestor test.txt@96b70246a118
warning: conflicts while merging test.txt! (edit, then use 'hg resolve --mark')
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
[1]
$ cat test.txt
one
<<<<<<< working copy: 50c3a7e29886 - test: Merge 1
two-point-five
=======
two-point-one
>>>>>>> merge rev: 40d11a4173a8 - test: two -> two-point-one
three
$ hg debugindex test.txt
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 7 ..... 0 01365c4cca56 000000000000 000000000000 (re)
1 7 9 ..... 1 7b013192566a 01365c4cca56 000000000000 (re)
2 16 15 ..... 2 8fe46a3eb557 01365c4cca56 000000000000 (re)
3 31 2. ..... 3 fc3148072371 7b013192566a 8fe46a3eb557 (re)
4 5. 25 ..... 4 d40249267ae3 8fe46a3eb557 000000000000 (re)
$ hg log
changeset: 4:40d11a4173a8
tag: tip
parent: 2:96b70246a118
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: two -> two-point-one
changeset: 3:50c3a7e29886
parent: 1:d1e159716d41
parent: 2:96b70246a118
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Merge 1
changeset: 2:96b70246a118
parent: 0:b1832b9d912a
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Numbers as words
changeset: 1:d1e159716d41
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 2 -> 2.5
changeset: 0:b1832b9d912a
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Initial
$ cd ..