Fix poor performance of to_tracking_manifest #1047
Merged
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This method had something like O(n^3) complexity because it would for
every tree in a manifest iterate over every tree in a manifest and
calculate the digest for every tree in the manifest (modulo short
circuiting).
Manifest::get_tree
is the culprit and an alternative technique ofcaching the mapping of digest to tree was added. Both uses of this
method have been updated but this method was left in place with a new
warning. It would be cheaper to call
get_tree
in a contrived casewhere the cache is only accessed once and not reused for multiple
lookups.
Fixes #1043.