share: fix typo to drop 'shared' requirement on unshare
This must be a typo and it seems correct to drop the requirement since the
repo is no longer a shared repository.
similar: compare between actual file contents for exact identity
Before this patch, similarity detection logic (for addremove and
automv) depends entirely on SHA-1 digesting. But this causes incorrect
rename detection, if:
- removing file A and adding file B occur at same committing, and
- SHA-1 hash values of file A and B are same
This may prevent security experts from managing sample files for
SHAttered issue in Mercurial repository, for example.
https://security.googleblog.com/2017/02/announcing-first-sha1-collision.html
https://shattered.it/
Hash collision itself isn't so serious for core repository
functionality of Mercurial, described by mpm as below, though.
https://www.mercurial-scm.org/wiki/mpm/SHA1
This patch compares between actual file contents after hash comparison
for exact identity.
Even after this patch, SHA-1 is still used, because it is reasonable
enough to quickly detect existence of "(almost) same" file.
- replacing SHA-1 causes decreasing performance, and
- replacement of it has ambiguity, yet
Getting content of removed file (= rfctx.data()) at each exact
comparison should be cheap enough, even though getting content of
added one costs much.
======= ============== =====================
file fctx data() reads from
======= ============== =====================
removed filectx in-memory revlog data
added workingfilectx storage
======= ============== =====================
localrepo: handle rename with hardlinks properly
In "aftertrans", we rename "journal.*" to "undo.*". We expect "journal.*"
files to disappear after renaming.
However, if "journal.foo" and "undo.foo" refer to a same file (hardlink),
rename may be a no-op, leaving both files on disk, according to Linux
manpage [1]:
If oldpath and newpath are existing hard links referring to the same
file, then rename() does nothing, and returns a suc‐ cess status.
The POSIX specification [2] is not very clear about what to do.
To be safe, remove "undo.*" before the rename so "journal.*" cannot be left
on disk.
[1]: http://man7.org/linux/man-pages/man2/rename.2.html
[2]: http://pubs.opengroup.org/onlinepubs/
9699919799/