Address gitlab API special character restrictions

[jsheunis]

The main change is from _repo_ to repo. This PR serves as a space to brainstorm an effective solution.

Closes #6681

[adswa]

The verdict from the discussion in the chat was:

• rename _repo_ to project (by default, and config item to redefine it. It should be config, because it would need to be set within a dataset, to avoid users having to remember it each and every time)
• replace the hierarchy separator -- with - (again with config item)

It should be configurations so that users themselves can act when GitLabs requirements change.

[adswa]

Also TODO:

• adjust test (it tests for a specific _repo_ name

[yarikoptic]

• replace the hierarchy separator -- with - (again with config item)

FTR: I tried to create test--name-with--dashes project on salsa of debian and got "Path must not start or end with a special character and must not contain consecutive special characters."

[adswa]

FTR: I tried to create test--name-with--dashes project on salsa of debian and got "Path must not start or end with a special character and must not contain consecutive special characters."

yes, this was the motivation behind not using -- as a path separator anymore. But if a user has a local dataset with this pattern, it would still fail. I think we should detect this and rename it, too...

[mih]

I think this makes all sense. I left a bunch of comments and suggestions, some even on stuff that is only in the margin of the diffs.

The PR top-comment should mention that this closes #6681 (12 months old).

[jsheunis]

Comments

1. Specification of the path separator via configuration datalad.gitlab-default-pathseparator should currently be done recursively in order to work correctly for subdatasets. For some other arguments set via config, the existing code infers the default from the top-level dataset (refds), and I think this should be the case for pathsep as well. I have made code suggestions to this effect.
2. This is more a question and explanation of my thoughts: it is not clear to me where exactly the path separator should be injected in a project's path. E.g. should it be injected twice when representing the path for a 2nd-level subdataset? And twice when representing a subdataset that's inside a subdirectory of the parent dataset? I tested out some examples below with separator="+" (note that the datasets all have dashes in them, just to add unnecessary complexity :D)
   • It seems like the collection path separation is done correctly (although this should actually be tested with even deeper levels)
   • It looks like the flat path separation is wrong though, shouldn't all dashes after BOB2 be replaced with the +?

Dataset structure

BOB
.
├── gitlab-subtest (dataset)
│   └── gitlab-subsub (dataset)
└── subdir (directory)
    └── gitlab-subdirdataset (dataset)

Collection example - BOB1

Flat example - BOB2

[jsheunis]

A note in case we have not seen this error before: I tried to specify the path separator as ~ and received the following error:

[Failed to create GitLab project: GitlabCreateError(400: {'name': ["can contain only letters, digits, emojis, '_', '.', '+', dashes, or spaces. It must start with a letter, digit, emoji, or '_'."]})]

[codeclimate]

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[adswa]

I have applied the suggestions from the review, adjusted the path-separator override test, and squashed a few commits together. Thanks, @mih and @jsheunis!

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.06 ⚠️

Comparison is base (425a8f7) 91.59% compared to head (eaa6fe8) 91.54%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7407      +/-   ##
==========================================
- Coverage   91.59%   91.54%   -0.06%     
==========================================
  Files         325      325              
  Lines       43318    43338      +20     
  Branches     5781     5806      +25     
==========================================
- Hits        39679    39675       -4     
- Misses       3624     3648      +24     
  Partials       15       15              

Impacted Files	Coverage Δ
datalad/distributed/create_sibling_gitlab.py	69.27% <100.00%> (+0.37%)	⬆️
...ad/distributed/tests/test_create_sibling_gitlab.py	98.62% <100.00%> (+0.12%)	⬆️

... and 30 files with indirect coverage changes

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[adswa]

Tests have passed!

[yarikoptic-gitmate]

PR released in 0.19.0