Move 'done' labels up so that if got_diffreg_output() fails we still call got_diffreg_result_free() instead of jumping straight over it. ok + fix from stsp@

Add new got_diff_blob_cb() implementation to compute added/removed line metrics for a given diff. This enables displaying a diffstat with 'got log -d'. As per suggestion from stsp, change tog diff view to display the diffstat by default. ok stsp@

pushed by mistake, wasn't reviewed.

diff from Josiah Frentsos and clue from tb@, thanks! (I can't read.)

based on a diff by Josiah Frentsos, thanks!

diff from Josiah Frentsos, thanks!

diff from Josiah Frentsos, thanks!

diff from Josiah Frentsos, thanks!

To avoid calling functions from got_operations.c directly from a template (which would hide the error), change got_output_repo_diff into got_open_diff_for_output that returns a file with the diff in it, to be then rendered by the template. got_gotweb_flushfile needs to be exposed then. It also bundles a smaller change: the `label' argument of got_repo_match_object_id is optional and not used, so just pass NULL there.

ok op@

was added there mistakenly. it's not part of the "compiler", it's part of the "user library" and provides useful functions for the consumers.