Support .gitignore as to tell which paths to not consider, or just consider git tracked files if under git

[yarikoptic]

When people upload from datalad datasets, they might have some incidental files already git ignored and it would be a surprise for them to upload some venvs/ etc. Possible logical ways are

• see if there is .gitignore where they should have ignored them .
  yet to check if could be used generally to query for each path similarly to how git check-attr could be used for .gitattributes.
• if dandiset is a git repository, consider only paths under git and ignore the rest by default (would need option to force somehow)

[jwodder]

@yarikoptic Alternative/additional feature proposed in standup: Support .ignore, used by ignore, ripgrep, ag, et alii.

[yarikoptic]

so is that .ignore -- where is it formalized? I googled into

• early announcement of it: https://geoff.greer.fm/2016/09/26/ignore/

but so far didn't run into clear specification. Pointer?

[jwodder]

@yarikoptic The only specification I can find is in the docs for ignore, which implements .ignore support for ripgrep:

.ignore files have the same semantics as gitignore files [1]

.gitignore files have match semantics as described in the gitignore man page. [2]

Does this suffice?

[yarikoptic]

oh, so it is .gitignore syntax...? I haven't realized that ... need to read/check more and see if it behaves "accordingly" .