From: Linus Torvalds <torvalds@osdl.org>
To: Daniel Barkalow <barkalow@iabervon.org>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
Rene Scharfe <rene.scharfe@lsrfire.ath.cx>,
Junio C Hamano <junkio@cox.net>,
git@vger.kernel.org
Subject: Re: A note on merging conflicts..
Date: Sat, 1 Jul 2006 15:57:42 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.0607011552170.12404@g5.osdl.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0607011754370.9789@iabervon.org>
On Sat, 1 Jul 2006, Daniel Barkalow wrote:
>
> I think a...b can be computed by (in pseudocode, obviously):
Nope.
> It's basically the original merge-bases code, from way back;
And it has basically the same bug.
It is possible to have
a
/ \
b c
|\ /|
d e f
\|/
g
and clearly "e" is the only valid merge-base of b and c.
HOWEVER. It's actually possible that we traverse d, f and g before we even
look at 'e' (because somebody had a bogus date, and 'e' _looks_ old).
Remember: in a distributed system we have no global clock, so any graph
traversal ordering we choose is by definition always arbitrary, even
though we can obviously _try_ to choose one that is efficient in practice
(ie the "sort the heap by date).
So that's why git-merge-base has all that extra "unnecessary" complexity.
You cannot output anything at all until you've guaranteed that all pending
objects are uninteresting.
Linus
next prev parent reply other threads:[~2006-07-01 22:57 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-01 2:44 A note on merging conflicts Linus Torvalds
2006-07-01 3:08 ` Junio C Hamano
2006-07-01 3:54 ` Linus Torvalds
2006-07-01 3:59 ` Linus Torvalds
2006-07-01 15:09 ` Rene Scharfe
2006-07-01 15:23 ` Johannes Schindelin
2006-07-01 16:25 ` Linus Torvalds
2006-07-01 18:13 ` Rene Scharfe
2006-07-01 18:01 ` J. Bruce Fields
2006-07-01 18:20 ` Linus Torvalds
2006-07-01 22:24 ` Daniel Barkalow
2006-07-01 22:57 ` Linus Torvalds [this message]
2006-07-01 23:25 ` Daniel Barkalow
2006-07-01 23:45 ` Daniel Barkalow
2006-07-02 11:31 ` Rene Scharfe
2006-07-02 21:42 ` Daniel Barkalow
2006-07-02 0:08 ` Linus Torvalds
2006-07-01 18:22 ` Jakub Narebski
2006-07-01 18:52 ` Linus Torvalds
2006-07-01 18:37 ` Junio C Hamano
2006-07-01 19:29 ` Rene Scharfe
2006-07-01 19:56 ` Junio C Hamano
2006-07-01 23:01 ` Johannes Schindelin
2006-07-01 20:04 ` Linus Torvalds
2006-07-01 20:07 ` Junio C Hamano
2006-07-01 20:14 ` Junio C Hamano
2006-07-01 23:29 ` [PATCH 1/3] Add get_merge_bases_clean() Rene Scharfe
2006-07-01 23:43 ` Johannes Schindelin
2006-07-01 23:29 ` [PATCH 2/3] Add '...' operator for revisions Rene Scharfe
2006-07-01 23:29 ` [PATCH 3/3] Make clear_commit_marks() clean harder Rene Scharfe
2006-07-03 9:32 ` Junio C Hamano
2006-07-03 13:56 ` Johannes Schindelin
2006-07-03 17:05 ` Linus Torvalds
2006-07-03 21:08 ` Johannes Schindelin
2006-07-03 19:47 ` Junio C Hamano
2006-07-03 21:12 ` Johannes Schindelin
2006-07-03 22:55 ` Linus Torvalds
2006-07-04 7:53 ` Johannes Schindelin
2006-07-04 8:20 ` Junio C Hamano
2006-07-02 9:49 ` [PATCH 4/3] Fold get_merge_bases_clean() into get_merge_bases() Rene Scharfe
2006-07-02 9:56 ` Johannes Schindelin
2006-07-02 16:43 ` Linus Torvalds
2006-07-02 17:40 ` Rene Scharfe
2006-07-02 18:28 ` Junio C Hamano
2006-07-02 20:59 ` Rene Scharfe
2006-07-02 21:15 ` Rene Scharfe
2006-07-02 21:17 ` Linus Torvalds
2006-07-02 20:44 ` Linus Torvalds
2006-07-07 8:26 ` A note on merging conflicts Junio C Hamano
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