Re: Implementing $Date$ substitution - problem with git status

[Johannes Sixt <j6t@kdbg.org>]

On Sonntag, 9. August 2009, Peter Krefting wrote:
> I finally got around to moving my web site repository over from CVS to Git,
> and to not have to redo everything about how it is set up, I set up a
> filter that fakes CVS' handling of "$Date$" keywords. Since I cannot access
> any information about the file from the "smudge" filter, I set up a "clean"
> filter that edits the $Date$ token on "git add":
>
>    #!/usr/bin/perl -wTp -i.bak
>    if (/\$Date:?[^\$]*\$/)
>    {
>      my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
> localtime(); my $now = sprintf("%04d-%02d-%02d %02d:%02d:%02d", $year +
> 1900, $mon + 1, $mday, $hour, $min, $sec);
>      s/\$Date:?[^\$]*\$/\$Date: ${now} \$/;
>    }
>
> In .gitattributes I have lines like:
>
>    *.html filter=date crlf=true ident
>
> and filter.date.clean is set to point to the script above in .git/config.
>
> This works fine, except that I have some problems with files that I cannot
> get to be "clean" in git status. "git diff" shows only a difference in the
> "$Date$" token, which is different each time I run "git diff" (the "+" line
> shows the current time):
>
>    diff --git a/.htaccess b/.htaccess
>    index 2dfbc32..d8ac343 100644
>    --- a/.htaccess
>    +++ b/.htaccess
>    @@ -2,7 +2,7 @@
>     # -----------------------------------------------------
>
>     # $Id$
>    -# $Date: 2009-08-09 19:52:30 $
>    +# $Date: 2009-08-09 20:31:56 $
>    [...]

The clean filter is applied before 'git diff' generates the diff. Since you 
have unstaged changes (I take [...] to mean this), you see a new date on 
every invocation.

After 'git add .htaccess' subsequent 'git diff' should not show any changes.

> Strangely, the $Id$ line above (which is handled by me adding the "ident"
> attribute to all text files), does not exhibit the same problem.
>
> Doing "git reset --hard" or "git checkout master filename" does not help,
> the file is still believed to be modified by git.

Now, that's an entirely different problem, and I think that there is a bug. I 
have observed this as well with my own clean filter sometimes, but not 
always. I haven't found a recipe that reliably exhibits the problem.

-- Hannes