[OE-core] [PATCH] buildhistory.bbclass: remove out-dated information on request

[Richard Purdie]

On Mon, 2016-02-08 at 07:56 +0100, Patrick Ohly wrote:
> buildhistory.bbclass by design is incremental: each build adds or
> updates information. Information is never removed.
> 
> Sometimes it can be useful to reduce the information only to those
> recipes that were build during a specific bitbake invocation, for
> example when the invocation does a full world build.
> 
> This is now possible by invoking bitbake with:
>    BB_ENV_EXTRAWHITE=BUILDHISTORY_REMOVE_OLD
> BUILDHISTORY_REMOVE_OLD=1 bitbake
> 
> In this mode, buildhistory.bbclass first moves all existing
> information into a temporary directory called "old" inside the build
> history directory. There the information is used for the "version
> going backwards QA check". Then when the build is complete and before
> (potentially) committing to git, the temporary directory gets
> deleted.
> 
> Because information that has not changed during the build will be
> reconstructed, a git log will then only show real updates, additions
> and removals.
> 
> Signed-off-by: Patrick Ohly <patrick.ohly at intel.com>

The implicit assumption here is that you'd only every build large
targets like "world". A "bitbake bash" isn't really going to do what
you'd expect/want.

I think we need to make that clearer in the comments and that this is
only useful on automated infrastructure.

Cheers,

Richard