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Kyle Lippincott's avatar
Kyle Lippincott authored
On some networked filesystems, writes can have delayed finalization/confirmation
and write races can occur such that a remote modification will "win" and
modifications will be lost. There is no functionality for providing this
feedback to userspace programs (in fact, there's not even functionality for
providing this information to the Linux kernel...), so these programs may see
the files suddenly change.

We've noticed that there have been cases where Mercurial has detected something
has gone wrong and attempts to abort (rolling back the transaction), which is
good. However, when rolling back the transaction, for the append-only files,
we attempt to "truncate" the file back to the size it was in before the hg
transaction started, but end up *extending* it. This may be harmless, but if
this happens to the 00changelog.i file, we get a bunch of nulls on the end of
the file and this causes hg to become *really* confused. :)

If we detect that some modification of the file outside of this Mercurial
process has caused the file to be smaller than the size we are attempting to
truncate to, let's just exit and stop trying to clean up the repository -
continuing will likely just cause more damage.

Differential Revision: https://phab.mercurial-scm.org/D6867
8502f76d
History
Name Last commit Last update
contrib
doc
hgdemandimport
hgext
hgext3rd
i18n
mercurial
relnotes
rust
tests
.arcconfig
.clang-format
.editorconfig
.hgignore
.hgsigs
.hgtags
.jshintrc
CONTRIBUTING
CONTRIBUTORS
COPYING
Makefile
README.rst
hg
hgeditor
hgweb.cgi
setup.py

Mercurial
=========

Mercurial is a fast, easy to use, distributed revision control tool
for software developers.

Basic install::

$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help

Running without installing::

$ make local # build for inplace usage
$ ./hg --version # should show the latest version

See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.