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* conda clean --lock: skip directories that don't exist, fixes 648
* fixed empty history file causing crash, issue 644
* remove timezone information from history file, fixes issue 651
* fix PackagesNotFound error for missing recursive dependencies
* change the default for adding cache from the local package cache -
known is now the default and the option to use index metadata from the
local package cache is --unknown
* add --alt-hint as a method to get an alternate form of a hint for
unsatisfiable packages
* add conda package --ls-files to list files in a package
* add ability to pin specs in an environment. To pin a spec, add a file
called pinned to the environment's conda-meta directory with the specs to
pin. Pinned specs are always kept installed, unless the --no-pin flag is
used.
* fix keyboard interrupting of external commands. Now keyboard interupting
conda build correctly removes the lock file
* add no_link ability to conda, see issue 678