bitbake: fetch2: Shorten long srcrevs

bitbake: fetch2: Shorten long srcrevs

The long srcrevs are mainly used or the workdir construction as well as
the package version. The long entries are hashes generated by the git fetcher
and other scms using a similar revision mechanism.

We need these to change when the package changes however collisions are
unlikely to happen within the domains we care about. The long revisions
have generated negative user feedback due to the use in path and file
names.

This patch therefore truncates the revisions to 10 characters maximum.

This should be safe in the contexts where these revisions are used as
the chances of spatially close collisions is very low (distant
collisions are not a major issue in the way we use these).

(Bitbake rev: 43a8319cda7fae37862dae323eeb24cb39ca21b7)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>