Geert Bosch <bosch@xxxxxxxxxxx> wrote:
> Such special magic based on filenames is always a bad idea. Tomorrow
> somebody
> comes with .zip files (oh, and of course .ZIP), then it's .jpg's other
> compressed content. In the end git will be doing lots of magic and
> still perform
> badly on unknown compressed content.
>
> There is a very simple way of detecting compressed files: just look
> at the
> size of the compressed blob and compare against the size of the
> expanded blob.
> If the compressed blob has a non-trivial size which is close to the
> expanded
> size, assume the file is not interesting as source or target for deltas.
>
> Example:
> if (compressed_size > expanded_size / 4 * 3 + 1024) {
> /* don't try to deltify if blob doesn't compress well */
> return ...;
> }
And yet I get good delta compression on a number of ZIP formatted
files which don't get good additional zlib compression (<3%).
Doing the above would cause those packfiles to explode to about
10x their current size.
--
Shawn.
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