fix(cli): fix dataset update with external files

[Panaetius]

closes #3363

[coveralls]

Pull Request Test Coverage Report for Build 5068211394

• 206 of 229 (89.96%) changed or added relevant lines in 14 files are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+21.3%) to 85.298%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
renku/core/dataset/dataset.py	29	32	90.63%
renku/core/dataset/providers/git.py	45	49	91.84%
renku/core/dataset/providers/api.py	42	47	89.36%
renku/core/dataset/providers/local.py	33	38	86.84%
renku/core/dataset/providers/web.py	41	47	87.23%

Files with Coverage Reduction	New Missed Lines	%
renku/ui/cli/init.py	1	96.9%
renku/ui/cli/service.py	1	68.59%

Totals
Change from base Build 5065889892:	21.3%
Covered Lines:	25730
Relevant Lines:	30165

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 4533833387

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

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Totals
Change from base Build 4529773607:	0.0%
Covered Lines:	0
Relevant Lines:	0

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💛 - Coveralls

[mohammad-alisafaee]

Thanks Ralf! This is great! I understand that the dataset part is quite confusing and it's good to have others to look into it. The refactoring you did is nice. Suggestions for more refactoring are welcome.

[mohammad-alisafaee]

Thanks Ralf! Please see my comments.

[mohammad-alisafaee]

Thank you!