view mercurial/help/diffs.txt @ 34144:91f0677dc920 stable

repair: preserve phase also when not using generaldelta (issue5678)

It seems like we used to pick the oldest possible version of the
changegroup to use for bundles created by the repair module (used
e.g. by "hg strip" and for temporary bundles by "hg rebase"). I tried
to preserve that behavior when I created the changegroup.safeversion()
method in 3b2ac2115464 (changegroup: introduce safeversion(),
2016-01-19).

However, we have recently chagned our minds and decided that these
commands are only used locally and downgrades are unlikely. That
decicion allowed us to start adding obsmarker and phase information to
these bundles. However, as the bug report shows, it means we get
different behavior e.g. when generaldelta is not enabled (because when
it was enabled, it forced us to use bundle2). The commit that actually
caused the reported bug was 8e3021fd1a44 (strip: include phases in
bundle (BC), 2017-06-15).

So, since we now depend on having more information in the bundles,
let's make sure we instead pick the newest possible changegroup
version.

Differential Revision: https://phab.mercurial-scm.org/D715

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.