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localrepo: iteratively derive local repository type...
localrepo: iteratively derive local repository type This commit implements the dynamic local repository type derivation that was explained in the recent commit bfeab472e3c0 "localrepo: create new function for instantiating a local repo object." Instead of a static localrepository class/type which must be customized after construction, we now dynamically construct a type by building up base classes/types to represent specific repository interfaces. Conceptually, the end state is similar to what was happening when various extensions would monkeypatch the __class__ of newly-constructed repo instances. However, the approach is inverted. Instead of making the instance then customizing it, we do the customization up front by influencing the behavior of the type then we instantiate that custom type. This approach gives us much more flexibility. For example, we can use completely separate classes for implementing different aspects of the repository. For example, we could have one class representing revlog-based file storage and another representing non-revlog based file storage. When then choose which implementation to use based on the presence of repo requirements. A concern with this approach is that it creates a lot more types and complexity and that complexity adds overhead. Yes, it is true that this approach will result in more types being created. Yes, this is more complicated than traditional "instantiate a static type." However, I believe the alternatives to supporting alternate storage backends are just as complicated. (Before I arrived at this solution, I had patches storing factory functions on local repo instances for e.g. constructing a file storage instance. We ended up having a handful of these. And this was logically identical to assigning custom methods. Since we were logically changing the type of the instance, I figured it would be better to just use specialized types instead of introducing levels of abstraction at run-time.) On the performance front, I don't believe that having N base classes has any significant performance overhead compared to just a single base class. Intuition says that Python will need to iterate the base classes to find an attribute. However, CPython caches method lookups: as long as the __class__ or MRO isn't changing, method attribute lookup should be constant time after first access. And non-method attributes are stored in __dict__, of which there is only 1 per object, so the number of base classes for __dict__ is irrelevant. Anyway, this commit splits up the monolithic completelocalrepository interface into sub-interfaces: 1 for file storage and 1 representing everything else. We've taught ``makelocalrepository()`` to call a series of factory functions which will produce types implementing specific interfaces. It then calls type() to create a new type from the built-up list of base types. This commit should be considered a start and not the end state. I suspect we'll hit a number of problems as we start to implement alternate storage backends: * Passing custom arguments to __init__ and setting custom attributes on __dict__. * Customizing the set of interfaces that are needed. e.g. the "readonly" intent could translate to not requesting an interface providing methods related to writing. * More ergonomic way for extensions to insert themselves so their callbacks aren't unconditionally called. * Wanting to modify vfs instances, other arguments passed to __init__. That being said, this code is usable in its current state and I'm convinced future commits will demonstrate the value in this approach. Differential Revision: https://phab.mercurial-scm.org/D4642

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phases.txt
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Matt Mackall
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r15996 What are phases?
FUJIWARA Katsunori
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r17267 ================
Matt Mackall
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r15996
Phases are a system for tracking which changesets have been or should
be shared. This helps prevent common mistakes when modifying history
(for instance, with the mq or rebase extensions).
Each changeset in a repository is in one of the following phases:
- public : changeset is visible on a public server
- draft : changeset is not yet published
- secret : changeset should not be pushed, pulled, or cloned
These phases are ordered (public < draft < secret) and no changeset
can be in a lower phase than its ancestors. For instance, if a
changeset is public, all its ancestors are also public. Lastly,
Johan Samyn
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r16244 changeset phases should only be changed towards the public phase.
Matt Mackall
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r15996
How are phases managed?
FUJIWARA Katsunori
doc: unify section level between help topics...
r17267 =======================
Matt Mackall
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r15996
For the most part, phases should work transparently. By default, a
changeset is created in the draft phase and is moved into the public
phase when it is pushed to another repository.
Once changesets become public, extensions like mq and rebase will
refuse to operate on them to prevent creating duplicate changesets.
Phases can also be manually manipulated with the :hg:`phase` command
if needed. See :hg:`help -v phase` for examples.
Matt Harbison
help: minor copy editing for grammar
r34950 To make your commits secret by default, put this in your
timeless
phases: mention how to make secret commits in help
r27514 configuration file::
[phases]
new-commit = secret
Matt Mackall
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r15996 Phases and servers
FUJIWARA Katsunori
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r17267 ==================
Matt Mackall
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r15996
Normally, all servers are ``publishing`` by default. This means::
- all draft changesets that are pulled or cloned appear in phase
public on the client
- all draft changesets that are pushed appear as public on both
client and server
- secret changesets are neither pushed, pulled, or cloned
.. note::
Simon Heimberg
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r20532
Matt Mackall
help: add phases topic
r15996 Pulling a draft changeset from a publishing server does not mark it
as public on the server side due to the read-only nature of pull.
Sometimes it may be desirable to push and pull changesets in the draft
phase to share unfinished work. This can be done by setting a
repository to disable publishing in its configuration file::
[phases]
Matt Mackall
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r16000 publish = False
Wagner Bruna
help/phases: remove trailing whitespace
r15998
Jordi Gutiérrez Hermoso
doc: reword "config file" to "configuration file"...
r19295 See :hg:`help config` for more information on configuration files.
Matt Mackall
help: add phases topic
r15996
.. note::
Simon Heimberg
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r20532
Matt Mackall
help: add phases topic
r15996 Servers running older versions of Mercurial are treated as
publishing.
Pierre-Yves David
phases: add a formal note that hash of secret changeset may leak out...
r20299 .. note::
Simon Heimberg
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r20532
Pierre-Yves David
phases: add a formal note that hash of secret changeset may leak out...
r20299 Changesets in secret phase are not exchanged with the server. This
applies to their content: file names, file contents, and changeset
metadata. For technical reasons, the identifier (e.g. d825e4025e39)
of the secret changeset may be communicated to the server.
Matt Mackall
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r16011 Examples
FUJIWARA Katsunori
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r17267 ========
Matt Mackall
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r16011
- list changesets in draft or secret phase::
hg log -r "not public()"
- change all secret changesets to draft::
hg phase --draft "secret()"
- forcibly move the current changeset and descendants from public to draft::
hg phase --force --draft .
Matt Harbison
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r34950 - show a list of changeset revisions and each corresponding phase::
Matt Mackall
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r16011
hg log --template "{rev} {phase}\n"
Matt Mackall
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r16041 - resynchronize draft changesets relative to a remote repository::
FUJIWARA Katsunori
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r19959 hg phase -fd "outgoing(URL)"
Matt Mackall
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r16041
Matt Mackall
help: add examples to phases topic
r16011 See :hg:`help phase` for more information on manually manipulating phases.