Re: [PATCHv2] git-mv: Keep moved index entries inact

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

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Hi,

On Mon, 28 Jul 2008, Junio C Hamano wrote:

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> 
> > On Mon, 28 Jul 2008, SZEDER Gábor wrote:
> >
> >> there is a race somewhere in these 'git-mv: Keep moved index entries
> >> inact' changes.
> >> 
> >> The test cases 'git mv should overwrite symlink to a file' or 'git mv
> >> should overwrite file with a symlink' fail occasionaly.  It's quite
> >> non-deterministic:  I have run t7001-mv.sh in a loop (see below) and
> >> one or the other usually fails around 50 runs (but sometimes only
> >> after 150).  Adding some tracing echos to the tests shows that both
> >> tests fail when running 'git diff-files' at the end.
> >
> > To make it more convenient to test: with this patch it fails all the time:
> 
> It's because we rename(2) but do not read back ctime, and reuse the cached
> data from the old path that was renamed.  After the failed test that moves
> a regular file "move" to "symlink":
> 
> $ stat symlink
>   File: `symlink'
>   Size: 2               Blocks: 8          IO Block: 4096   regular file
> Device: 30ah/778d       Inode: 18104337    Links: 1
> Access: (0664/-rw-rw-r--)  Uid: ( 1012/   junio)   Gid: (   40/     src)
> Access: 2008-07-28 11:49:55.000000000 -0700
> Modify: 2008-07-28 11:48:41.000000000 -0700
> Change: 2008-07-28 11:48:42.000000000 -0700
> 
> But the cached stat information looks like this:
> 
> $ ../../git-ls-files --stat
> ctime=1217270921, mtime=1217270921, ino=18104337, mode=100644, uid=1012, gid=40symlink
> 
> We need to refresh the entry to pick up potential ctime changes.

Yep.

Tested-by: me

BTW I have no idea how we could test for this, short of introducing the 
"sleep 1" I did earlier.  Maybe guard it with a TEST_EXPENSIVE_CTIME 
variable or something similar.  Dunno.

And my suggestion to use test-chmtime: please just forget about it, and 
just assume that I had some very good wiid(1) in my pipe(2).

Ciao,
Dscho