mercurial/help/diffs.txt

scmutil: make cleanupnodes optionally also fix the phase

We have had multiple bugs where the phase wasn't correctly carried
forward to a rewritten changeset (for example: phabricator, split,
evolve, fix). Handling the phase update in cleanupnodes() makes it
less likely to happen again, especially once we have made it fix the
phase by default (perhaps in the next release cycle).

This patch also updates all applicable callers so we get some testing
of it.

Note that rebase and histedit can't be fixed yet because they call
cleanupnodes() only at the end and the phase may have been changed by
the user when the rebase/histedit was interrupted (due to merge
conflicts). I think we should make them write one commit at a time (as
it already does), along with associated obsmarkers, bookmark moves,
etc. When that's done, we can switch them over to cleanupnodes().

Differential Revision: https://phab.mercurial-scm.org/D3818

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.