`dvc gc --time <datetime>`

[efiop]

#669

@dmpetrov :

the data time could be used for the garbage collector - very natural way to reduce size. dvc gc --time month - clean everything not from the current branch and older than a month.

[efiop]

Not sure about this, as not mtime on data files nor mtime on cache files is really indicative of the usage or lack of it. Plus, I don't see a good way that we will not break a particular pipeline with older files. Need to reconsider it later. Moving to 0.9.8 milestone.

[efiop]

More organic way would be to use git commits as a limiter. I.e. gc --time month will save data for all pipelines up to a week.

[efiop]

Moved to 0.11.0.