Re: What's cooking in git.git (Jun 2010, #04; Wed, 23)

Am 6/24/2010 22:21, schrieb Junio C Hamano:

Finn Arne Gangstad [off-list ref] writes:

quoted

If .gitattributes is different on the different sides, or if you
enable autocrlf, the current repo contents may change after
git-to-worktree and worktree-to-git again.

IOW, g2w-then-w2g may not be an identity function.

If we were to encourage use of this codepath to wider audiences, we may
need to have a document for people who write smudge/clean filters.  In
order for the result to be stable, applying g2w-then-w2g once again on top
of the result of running g2w-then-w2g on anything should be no-op, no?

I think this is implicit to some degree in the documentation,
gitattributes(5):

  The content filtering is done to massage the content into a shape that
  is more convenient for the platform, filesystem, and the user to use.
  [...] the intent is that if someone unsets the filter driver
  definition, or does not have the appropriate filter program, the
  project should still be usable.

From this I read that the content of the repository can only be in a

canonical shape; hence, the only thing that a clean filter can do is to
generate the canonical shape of the data. This is, by definition, an
idempotent operation (i.e., g2w(g2w(x)) == g2w(x)).

(I'm talking only about clean filters because any pair of smudge+clean
filters where the clean filter cannot undo the effect of the smudge filter
would be noticed immediately and be considered broken without being
mentioned explicitly in the documentation.)

-- Hannes