On Mon, Sep 24, 2018 at 02:15:30PM -0700, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <dsto...@microsoft.com>
>
> The index v4 format has been available since 2012 with 9d22778
> "reach-cache.c: write prefix-compressed names in the index". Since
> the format has been stable for so long, almost all versions of Git
> in use today understand version 4, removing one barrier to upgrade
> -- that someone may want to downgrade and needs a working repo.
What about alternative implementations, like JGit, libgit2, etc.?
> Despite being stable for a long time, this index version was never
> adopted as the default. This prefix-compressed version of the format
> can get significant space savings on repos with large working
> directories (which naturally tend to have deep nesting). This version
> is set as the default for some external tools, such as VFS for Git.
> Because of this external use, the format has had a lot of "testing in
> production" and also is subject to continuous integration in these
> environments.
>
> Previously, to test version 4 indexes, we needed to run the test
> suite with GIT_TEST_INDEX_VERSION=4 (or TEST_GIT_INDEX_VERSION=4).
>
> One potential, but short-term, downside is that we lose coverage of
> the version 3 indexes. The trade-off is that we may want to cover
> that version using GIT_TEST_INDEX_VERSION=3.
>
> Signed-off-by: Derrick Stolee <dsto...@microsoft.com>
> ---
> read-cache.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/read-cache.c b/read-cache.c
> index 372588260e..af6c8f2a67 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -1484,7 +1484,7 @@ struct cache_entry *refresh_cache_entry(struct
> cache_entry *ce,
> * Index File I/O
> *****************************************************************/
>
> -#define INDEX_FORMAT_DEFAULT 3
> +#define INDEX_FORMAT_DEFAULT 4
>
> static unsigned int get_index_format_default(void)
> {
> --
> gitgitgadget
