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parsers: fail fast if Python has wrong minor version (issue4110)...
parsers: fail fast if Python has wrong minor version (issue4110) This change causes an informative ImportError to be raised when importing the extension module parsers if the minor version of the currently-running Python interpreter doesn't match that of the Python that was used when compiling the extension module. Here is an example of what the new error looks like: Traceback (most recent call last): File "test.py", line 1, in <module> import mercurial.parsers ImportError: Python minor version mismatch: The Mercurial extension modules were compiled with Python 2.7.6, but Mercurial is currently using Python with sys.hexversion=33883888: Python 2.5.6 (r256:88840, Nov 18 2012, 05:37:10) [GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] at: /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/ Python.app/Contents/MacOS/Python The reason for raising an error in this scenario is that Python's C API is known not to be compatible from minor version to minor version, even if sys.api_version is the same. See for example this Python bug report about incompatibilities between 2.5 and 2.6+: http://bugs.python.org/issue8118 These incompatibilities can cause Mercurial to break in mysterious, unforeseen ways. For example, when Mercurial compiled with Python 2.7 was run with 2.5, the following crash occurred when running "hg status": http://bz.selenic.com/show_bug.cgi?id=4110 After this crash was fixed, running with Python 2.5 no longer crashes, but the following puzzling behavior still occurs: $ hg status ... File ".../mercurial/changelog.py", line 123, in __init__ revlog.revlog.__init__(self, opener, "00changelog.i") File ".../mercurial/revlog.py", line 251, in __init__ d = self._io.parseindex(i, self._inline) File ".../mercurial/revlog.py", line 158, in parseindex index, cache = parsers.parse_index2(data, inline) TypeError: data is not a string which can be reproduced more simply with: import mercurial.parsers as parsers parsers.parse_index2("", True) Both the crash and the TypeError occurred because the Python C API's PyString_Check returns the wrong value when the C header files from Python 2.7 are run with Python 2.5. This is an example of an incompatibility of the sort mentioned in the Python bug report above. Failing fast with an informative error message will result in a better user experience in cases like the above. The information in the ImportError will also simplify troubleshooting for those on Mercurial mailing lists, the bug tracker, etc. This patch only adds the version check to parsers.c, which is sufficient to affect command-line commands like "hg status" and "hg summary". An idea for a future improvement is to move the version-checking C code to a more central location, and have it run when importing all Mercurial extension modules and not just parsers.c.

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====
hg
====
---------------------------------------
Mercurial source code management system
---------------------------------------
:Author: Matt Mackall <mpm@selenic.com>
:Organization: Mercurial
:Manual section: 1
:Manual group: Mercurial Manual
.. contents::
:backlinks: top
:class: htmlonly
:depth: 1
Synopsis
""""""""
**hg** *command* [*option*]... [*argument*]...
Description
"""""""""""
The **hg** command provides a command line interface to the Mercurial
system.
Command Elements
""""""""""""""""
files...
indicates one or more filename or relative path filenames; see
`File Name Patterns`_ for information on pattern matching
path
indicates a path on the local machine
revision
indicates a changeset which can be specified as a changeset
revision number, a tag, or a unique substring of the changeset
hash value
repository path
either the pathname of a local repository or the URI of a remote
repository.
.. include:: hg.1.gendoc.txt
Files
"""""
``/etc/mercurial/hgrc``, ``$HOME/.hgrc``, ``.hg/hgrc``
This file contains defaults and configuration. Values in
``.hg/hgrc`` override those in ``$HOME/.hgrc``, and these override
settings made in the global ``/etc/mercurial/hgrc`` configuration.
See |hgrc(5)|_ for details of the contents and format of these
files.
``.hgignore``
This file contains regular expressions (one per line) that
describe file names that should be ignored by **hg**. For details,
see |hgignore(5)|_.
``.hgsub``
This file defines the locations of all subrepositories, and
tells where the subrepository checkouts came from. For details, see
:hg:`help subrepos`.
``.hgsubstate``
This file is where Mercurial stores all nested repository states. *NB: This
file should not be edited manually.*
``.hgtags``
This file contains changeset hash values and text tag names (one
of each separated by spaces) that correspond to tagged versions of
the repository contents. The file content is encoded using UTF-8.
``.hg/last-message.txt``
This file is used by :hg:`commit` to store a backup of the commit message
in case the commit fails.
``.hg/localtags``
This file can be used to define local tags which are not shared among
repositories. The file format is the same as for ``.hgtags``, but it is
encoded using the local system encoding.
Some commands (e.g. revert) produce backup files ending in ``.orig``,
if the ``.orig`` file already exists and is not tracked by Mercurial,
it will be overwritten.
Bugs
""""
Probably lots, please post them to the mailing list (see Resources_
below) when you find them.
See Also
""""""""
|hgignore(5)|_, |hgrc(5)|_
Author
""""""
Written by Matt Mackall <mpm@selenic.com>
Resources
"""""""""
Main Web Site: http://mercurial.selenic.com/
Source code repository: http://selenic.com/hg
Mailing list: http://selenic.com/mailman/listinfo/mercurial
Copying
"""""""
Copyright (C) 2005-2013 Matt Mackall.
Free use of this software is granted under the terms of the GNU General
Public License version 2 or any later version.
.. include:: common.txt