view mercurial/help/diffs.txt @ 27764:dd0c5f4d1b53

util: adjust 'datapath' to be correct in a frozen OS X package

Apparently unlike py2exe, py2app copies the Mercurial source tree as-is to a
Contents/Resources subdirectory of an app bundle, and places its binary stub in
Contents/MacOS.  (The Windows install has the 'hgext' and 'mercurial' modules in
'lib/library.zip', while the help and templates subdirectories have been moved
out of the mercurial directory to the root of the installation.  I assume that
the python code living in a zip file is why "py2exe doesn't support __file__".)
Therefore, prior to this change, Mercurial in a frozen app bundle on OS X would
go looking for help *.txt, templates and locale info in Contents/MacOS, where
they don't exist.

There are only a handful of places that test for frozen, and not all of them are
wrong for OS X, so it seems wiser to handle them on a case by case basis, rather
that try to change mainfrozen().  The remaining cases are:

  1) util.hgexecutable() wrongly points to the bundled python executable, and
       affects $HG in util.system() launched processes (e.g. external hooks)
  2) util.hgcmd() wrongly points to the bundled python executable, but it seems
       to only affect 'hg serve -d'
  3) hook._pythonhook() may be OK, since I didn't see anything outrageous when
       printing sys.path from an internal hook.  I'm not sure if this special
       case is needed on OS X though.
  4) sslutil._plainapplepython() is OK, because sys.executable is not
       /usr/bin/python, nor is it in /System/Library/Frameworks

Mercurial's default format for showing changes between two versions of
a file is compatible with the unified format of GNU diff, which can be
used by GNU patch and many other standard tools.

While this standard format is often enough, it does not encode the
following information:

- executable status and other permission bits
- copy or rename information
- changes in binary files
- creation or deletion of empty files

Mercurial also supports the extended diff format from the git VCS
which addresses these limitations. The git diff format is not produced
by default because a few widespread tools still do not understand this
format.

This means that when generating diffs from a Mercurial repository
(e.g. with :hg:`export`), you should be careful about things like file
copies and renames or other things mentioned above, because when
applying a standard diff to a different repository, this extra
information is lost. Mercurial's internal operations (like push and
pull) are not affected by this, because they use an internal binary
format for communicating changes.

To make Mercurial produce the git extended diff format, use the --git
option available for many commands, or set 'git = True' in the [diff]
section of your configuration file. You do not need to set this option
when importing diffs in this format or using them in the mq extension.