convert: don't drop missing or corrupt tag entries
Cleaning up the tags file could be a useful feature in some cases, so maybe
there should be a switch for this. However, the default hg -> hg convert tries
to maintain identical hashes (thus convert.hg.saverev is off by default, but is
on by default for other source types). It looks like _rewritesubstate() has a
`continue` in it, and therefore a similar problem.
I ran into this conversion divergence when a coworker "merged" two repositories
by copy/pasting all of the files from the source repo and massaging the code,
and forgetting to revert the .hg* files. That silently emptied the .hgtags file
after the conversion. (This isn't the manifest node bug Yuya has been helping
with- this occurred well after the bzr -> hg conversion and wasn't a merge
commit, which made it extra puzzling. That bug is still an issue.)
All config options used within Mercurial should be registered.
Config Option in Core
=====================
Config options used by Mercurial core are registered in the
``mercurial.configitems`` module.
Simple entry
------------
A registration entry typically looks like::
coreconfigitem('section', 'option',
default=MyDefaultValue,
)
Once registered, Mercurial will know that ``section.option`` is a legitimate
config option and that ``MyDefaultValue`` should be used if no other values are
defined in configuration files.
Complex default value
---------------------
If the default provided is a callable, it is called to retrieve the default
value when accessing the config option. This is useful for default values that
are mutable like the empty list::
coreconfigitem('pager', 'ignore',
default=list,
)
In addition, there are cases where the default is not fixed, but computed from
other properties. In this case, use the ``dynamicdefault`` object as the value
for the ``default`` parameter. A default value is then explicitly required when
reading the option::
# registration
coreconfigitem('web', 'name',
default=dynamicdefault,
)
# usage
ui.config('web', 'name', dirname)
Free form options
-----------------
Some config sections use free form options (e.g. ``paths``). You can register
them using the ``generic`` parameters::
coreconfigitem('paths', '.*',
default=None,
generic=True,
)
When ``generic=True`` is set, the option name is matched as a regular expression
(rooted to string start). It can be used to select specific sub parameters::
coreconfigitem('merge-tools', br'.*\.args$',
default="$local $base $other",
generic=True,
priority=-1,
)
The ``priority`` parameter controls the order used to match the generic pattern
(lower first).
Config Option in Extensions
===========================
General case
------------
Extensions should register config items through the ``registrar`` API (also used
for commands and others)::
configtable = {}
configitem = registrar.configitem(configtable)
configitem('blackbox', 'dirty',
default=False,
)
The ``dynamicdefault`` object is then available as
``configitem.dynamicdefault``.
Supporting older versions
-------------------------
The registrar was introduced in Mercurial 4.3, and the ``generic`` parameter was
introduced in 4.4. Starting with Mercurial 4.4, all core options were registered
and developer warnings are emitted when accessing unregistered option.
Extensions supporting versions older than Mercurial 4.3 cannot rely on the
default value being registered. The simplest way to register an option while
still supporting an older version is to use ``dynamicdefault`` for options
requiring a default value. The existing code passing an explicit default can
then stay in use until compatibility with Mercurial 4.2 is dropped.
As reminder, here are the default values for each config type:
- config: None
- configbool: False
- configbytes: 0
- configdate: None
- configint: None
- configlist: []
- configpath: None