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streamclone: define first iteration of version 2 of stream format...
streamclone: define first iteration of version 2 of stream format (This patch is based on a first draft from Gregory Szorc, with deeper rework) Version 1 of the stream clone format was invented many years ago and suffers from a few deficiencies: 1) Filenames are stored in store-encoded (on filesystem) form rather than in their internal form. This makes future compatibility with new store filename encodings more difficult. 2) File entry "headers" consist of a newline of the file name followed by the string file size. Converting strings to integers is avoidable overhead. We can't store filenames with newlines (manifests have this limitation as well, so it isn't a major concern). But the big concern here is the necessity for readline(). Scanning for newlines means reading ahead and that means extra buffer allocations and slicing (in Python) and this makes performance suffer. 3) Filenames aren't compressed optimally. Filenames should be compressed well since there is a lot of repeated data. However, since they are scattered all over the stream (with revlog data in between), they typically fall outside the window size of the compressor and don't compress. 4) It can only exchange stored based content, being able to exchange caches too would be nice. 5) It is limited to a stream-based protocol and isn't suitable for an on-disk format for general repository reading because the offset of individual file entries requires scanning the entire file to find file records. As part of enabling streaming clones to work in bundle2, #2 proved to have a significant negative impact on performance. Since bundle2 provides the opportunity to start fresh, Gregory Szorc figured he would take the opportunity to invent a new streaming clone data format. The new format devised in this series addresses #1, #2, and #4. It punts on #3 because it was complex without yielding a significant gain and on #5 because devising a new store format that "packs" multiple revlogs into a single "packed revlog" is massive scope bloat. However, this v2 format might be suitable for streaming into a "packed revlog" with minimal processing. If it works, great. If not, we can always invent stream format when it is needed. This patch only introduces the bases of the format. We'll get it usable through bundle2 first, then we'll extend the format in future patches to bring it to its full potential (especially #4).

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urls.txt
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Valid URLs are of the form::
local/filesystem/path[#revision]
file://local/filesystem/path[#revision]
http://[user[:pass]@]host[:port]/[path][#revision]
https://[user[:pass]@]host[:port]/[path][#revision]
ssh://[user@]host[:port]/[path][#revision]
Paths in the local filesystem can either point to Mercurial
repositories or to bundle files (as created by :hg:`bundle` or
:hg:`incoming --bundle`). See also :hg:`help paths`.
An optional identifier after # indicates a particular branch, tag, or
changeset to use from the remote repository. See also :hg:`help
revisions`.
Some features, such as pushing to http:// and https:// URLs are only
possible if the feature is explicitly enabled on the remote Mercurial
server.
Note that the security of HTTPS URLs depends on proper configuration of
web.cacerts.
Some notes about using SSH with Mercurial:
- SSH requires an accessible shell account on the destination machine
and a copy of hg in the remote path or specified with as remotecmd.
- path is relative to the remote user's home directory by default. Use
an extra slash at the start of a path to specify an absolute path::
ssh://example.com//tmp/repository
- Mercurial doesn't use its own compression via SSH; the right thing
to do is to configure it in your ~/.ssh/config, e.g.::
Host *.mylocalnetwork.example.com
Compression no
Host *
Compression yes
Alternatively specify "ssh -C" as your ssh command in your
configuration file or with the --ssh command line option.
These URLs can all be stored in your configuration file with path
aliases under the [paths] section like so::
[paths]
alias1 = URL1
alias2 = URL2
...
You can then use the alias for any command that uses a URL (for
example :hg:`pull alias1` will be treated as :hg:`pull URL1`).
Two path aliases are special because they are used as defaults when
you do not provide the URL to a command:
default:
When you create a repository with hg clone, the clone command saves
the location of the source repository as the new repository's
'default' path. This is then used when you omit path from push- and
pull-like commands (including incoming and outgoing).
default-push:
The push command will look for a path named 'default-push', and
prefer it over 'default' if both are defined.