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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
Xavier Lepaul - - Load All Authors

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Matt Harbison
help: attempt to clarify that pager usage is not output length based...
 r32138 Some Mercurial commands can produce a lot of output, and Mercurial will
Augie Fackler
pager: move most help to a new help topic and deprecate extension
 r31061 attempt to use a pager to make those commands more pleasant.
To set the pager that should be used, set the application variable::
[pager]
pager = less -FRX
Xavier Lepaul
help: clarify the choice of pager...
 r32608 If no pager is set in the user or repository configuration, Mercurial uses the
environment variable $PAGER. If $PAGER is not set, pager.pager from the default
or system configuration is used. If none of these are set, a default pager will
be used, typically `less` on Unix and `more` on Windows.
Augie Fackler
pager: move most help to a new help topic and deprecate extension
 r31061
Matt Harbison
help: document color/pager pitfalls on Windows...
 r32137 .. container:: windows
On Windows, `more` is not color aware, so using it effectively disables color.
MSYS and Cygwin shells provide `less` as a pager, which can be configured to
support ANSI color codes. See :hg:`help config.color.pagermode` to configure
the color mode when invoking a pager.
Augie Fackler
pager: move most help to a new help topic and deprecate extension
 r31061 You can disable the pager for certain commands by adding them to the
pager.ignore list::
[pager]
ignore = version, help, update
To ignore global commands like :hg:`version` or :hg:`help`, you have
to specify them in your user configuration file.
To control whether the pager is used at all for an individual command,
FUJIWARA Katsunori
help: apply bulk fixes for indentation and literal blocking issues...
 r32085 you can use --pager=<value>:
Augie Fackler
pager: move most help to a new help topic and deprecate extension
 r31061
- use as needed: `auto`.
- require the pager: `yes` or `on`.
- suppress the pager: `no` or `off` (any unrecognized value
FUJIWARA Katsunori
help: apply bulk fixes for indentation and literal blocking issues...
 r32085 will also work).
Augie Fackler
pager: add a config knob to just globally turn off the pager
 r31062
To globally turn off all attempts to use a pager, set::
Pierre-Yves David
pager: rename 'pager.enable' to 'ui.paginate'...
 r32105 [ui]
paginate = never
Augie Fackler
pager: add a config knob to just globally turn off the pager
 r31062
which will prevent the pager from running.