view mercurial/help/diffs.txt @ 23167:a3c2d9211294 stable

templater: don't overwrite the keyword mapping in runsymbol() (issue4362)

This keyword remapping was introduced in e06e9fd2d99f as part of converting
generator based iterators into list based iterators, mentioning "undesired
behavior in template" when a generator is exhausted, but doesn't say what and
introduces no tests.

The problem with the remapping was that it corrupted the output for keywords
like 'extras', 'file_copies' and 'file_copies_switch' in templates such as:

    $ hg log -r 142b5d5ec9cc --template "{file_copies % ' File: {file_copy}\n'}"
    File: mercurial/changelog.py (mercurial/hg.py)
    File: mercurial/changelog.py (mercurial/hg.py)
    File: mercurial/changelog.py (mercurial/hg.py)
    File: mercurial/changelog.py (mercurial/hg.py)
    File: mercurial/changelog.py (mercurial/hg.py)
    File: mercurial/changelog.py (mercurial/hg.py)
    File: mercurial/changelog.py (mercurial/hg.py)
    File: mercurial/changelog.py (mercurial/hg.py)

What was happening was that in the first call to runtemplate() inside runmap(),
'lm' mapped the keyword (e.g. file_copies) to the appropriate showxxx() method.
On each subsequent call to runtemplate() in that loop however, the keyword was
mapped to a list of the first item's pieces, e.g.:

   'file_copy': ['mercurial/changelog.py', ' (', 'mercurial/hg.py', ')']

Therefore, the dict for the second and any subsequent items were not processed
through the corresponding showxxx() method, and the first item's data was
reused.

The 'extras' keyword regressed in de7e6c489412, and 'file_copies' regressed in
0b241d7a8c62 for other reasons.  The common thread of things fixed by this seems
to be when a list of dicts are passed to the templatekw._hybrid class.

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.