enable saving of hashes w/abundances in multigather --output-unassigned

[ctb]

In #1392, I noticed that in src/sourmash/commands.py, function multigather, that abundances are not saved when unassigned hashes are output. See code block starting with with open(output_unassigned, 'wt') as fp:.

TODO:

• look at the code in gather, and copy the code block to reinflate abundances over to multigather;
• write tests for this feature of multigather (probably starting with the relevant test for gather, which is test_gather_output_unassigned_with_abundance)

This could wait until after #1463 is fixed, or be done in the same PR as that issue.

[keyabarve]

@ctb I'd like to work on this issue.

[ctb]

On Sat, Jun 12, 2021 at 04:10:42PM -0700, Keya Barve wrote: @ctb I'd like to work on this issue.

sure! generally you should signal that by creating a pull request (even if incomplete) and linking to it from the issue.

[keyabarve]

@ctb Should #1463 be resolved before working on this?

[ctb]

This could wait until after #1463 is fixed, or be done in the same PR as that issue.

After, or during, either way.

[keyabarve]

@ctb Is this issue the same as #1707?

[ctb]

yep! closing as duplicate.