Re: Adding a new file as if it had existed

"Bahadir Balban" [off-list ref] writes:

... I said "performance reasons" assuming all the
file hashes need checked for every commit -a to see if they're
changed, but I just tried on a PIII and it seems not so slow.

Ok.

Other people have already cleared the fear for 'commit' case, so
I hope you are happier.

There is one thing we could further optimize, though.

Switching branches with 100k blobs in a commit even when there
are a handful paths different between the branches would still
need to populate the index by reading two trees and collapsing
them into a single stage.  In theory, we should be able to do a
lot better if two-tree case of read-tree took advanrage of
cache-tree information.  If ce_match_stat() says Ok for all
paths in a subdirectory and the cached tree object name for that
subdirectory in the index match what we are reading from the new
tree, we should be able to skip reading that subdirectory (and
its subdirectories) from the new tree object at all.

Anybody interested to give it a try?