patchgit-archive documentation: .gitattributes must be committed

> Add a note to the documentation stating that the .gitattributes
> file must be present (i.e. committed) in the named tree that is
> exported.
> 
> This can be a bit confusing because it's different from .gitignore
> which takes effect as soon as the file is created.
> 
> Signed-off-by: Francois Marier <fmarier@gmail.com>
> ---
>  Documentation/git-archive.txt |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/git-archive.txt b/Documentation/git-archive.txt
> index 799c8b6..fcd681d 100644
> --- a/Documentation/git-archive.txt
> +++ b/Documentation/git-archive.txt
> @@ -112,6 +112,9 @@ export-subst::
>  	expand several placeholders when adding this file to an archive.
>  	See linkgit:gitattributes[5] for details.
>  
> +The .gitattributes file must be present in the named tree for it to take
> +effect. Uncommitted attributes will not be considered in exports.
> +
>  EXAMPLES
>  --------
>  git archive --format=tar --prefix=junk/ HEAD | (cd /var/tmp/ && tar xf -)::

>> +The .gitattributes file must be present in the named tree for it to take
>> +effect. Uncommitted attributes will not be considered in exports.
>> +
>>  EXAMPLES
>>  --------
>>  git archive --format=tar --prefix=junk/ HEAD | (cd /var/tmp/ && tar xf -)::
>
> Yeah, the description of --worktree-attributes is a bit terse.  The
> lines you add make it appear almost as if this switch doesn't exist,
> though; perhaps add a "unless --worktree-attributes is given" or similar
> to one of the new sentences?

> By the way, if you commit the attributes file, then commit the removal of
> that attributes file, would that removed attributes file take effect when
> you archive HEAD^ (which still had the attribues file)?  That's how I read
> what the added description claims, but I somehow suspect that is not what
> actually happens.

> René Scharfe <rene.scharfe@lsrfire.ath.cx> writes:
> 
>>> +The .gitattributes file must be present in the named tree for it to take
>>> +effect. Uncommitted attributes will not be considered in exports.
>>> +
>>>  EXAMPLES
>>>  --------
>>>  git archive --format=tar --prefix=junk/ HEAD | (cd /var/tmp/ && tar xf -)::
>>
>> Yeah, the description of --worktree-attributes is a bit terse.  The
>> lines you add make it appear almost as if this switch doesn't exist,
>> though; perhaps add a "unless --worktree-attributes is given" or similar
>> to one of the new sentences?
> 
> My impression has always been that people use attributes with archive more
> often to _tweak_ how the archive is produced after the fact, and they do
> so by modifying checked out .gitattributes (or $GIT_DIR/info/attributes)
> than allowing a possibly stale .gitattributes file etched in stone^Wtree
> being archived.  So in that sense, probably --worktree-attributes should
> have been the default.

> René Scharfe <rene.scharfe@lsrfire.ath.cx> writes:
>
>> ...  I think that the current
>> behaviour makes sense because it provides a repeatable default.
>
> I wouldn't insist on changing the default again too strongly, but I think
> the --worktree-attributes option should be advertised better in the
> documentation, as that mode of operation seems to match what the users
> expect better, and I think that is how this thread started.

> +Note that attributes are by default taken from the `.gitattributes` files
> +in the tree that is being archived.  If you want to tweak the way the
> +output is generated after the fact (e.g. you committed without adding an
> +appropriate export-ignore in its `.gitattributes`), adjust the checked out
> +`.gitattributes` file as necessary and use `--work-tree-attributes`
> +option.  Alternatively you can keep necessary attributes that should apply
> +while archiving any tree in your `$GIT_DIR/info/attributes` file.