[REF] Replaces master with main where possible

[jbteves]

Addresses but does not close #619 .

Changes proposed in this pull request:

• Switch master to main where applicable

NOTE: due to versioneer and the document doc tree, there are some references to master that cannot be changed from my read. All examples below:

docs/conf.py:67:# The master toctree document.
docs/conf.py:68:master_doc = 'index'
docs/governance.rst:184:`decision-making rules for the BIDS standard <https://github.com/bids-standard/bids-specification/blob/master/DECISION-MAKING.md>`_,
tedana/_version.py:192:        # "stabilization", as well as "HEAD" and "master".
versioneer.py:18:(https://travis-ci.org/warner/python-versioneer.png?branch=master)
versioneer.py:179:  "master" and "slave" subprojects, each with their own `setup.py`,
versioneer.py:612:        # "stabilization", as well as "HEAD" and "master".
versioneer.py:1004:        # "stabilization", as well as "HEAD" and "master".

[codecov]

Codecov Report

Merging #667 (f5d3913) into master (74b922d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #667   +/-   ##
=======================================
  Coverage   93.75%   93.75%           
=======================================
  Files          26       26           
  Lines        2019     2019           
=======================================
  Hits         1893     1893           
  Misses        126      126           

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[tsalo]

LGTM. Thanks for doing this.

[emdupre]

Thanks for this, @jbteves !

I'm getting three external links that don't (yet) resolve with main, so I think we'll need to revert those changes for now. But overall, very happy to have this updated !!

[jbteves]

Oh, silly me, good catches @emdupre !

[jbteves]

I think the issue was that at some point GitHub had stated they would redirect main and master correctly for you, but I didn't check and it seems that's not implemented. My fault for not checking.

[emdupre]

I think the issue was that at some point GitHub had stated they would redirect main and master correctly for you, but I didn't check and it seems that's not implemented. My fault for not checking.

No worries ! I was confused on that too -- the scikit link redirects correctly from master to main, but I think that's only because they've made a main branch already. The remaining links still only have the master branch, it seems. Regardless, I think these changes are now ready to go !

[jbteves]

So my plan to proceed, once we have approvals, is to do the following:

• Merge this PR.
• Throw the switch from master to main.
• Pin Set default branch to main #619 , with the top comment edited with the instructions and reiterating that I'm the point of contact if developers need help.
• If issues arise, try to tackle them tonight.

If there's no objections, then pending the additional review from @tsalo I'll go ahead.

EDIT: Actually, I don't have permission to throw the switch, so either I need to be granted permission or someone else will need to.

[eurunuela]

LGTM! Thank you @jbteves . If we miss something we'll see after merging anyway. I'll be checking my notifications in case you need any help.

[tsalo]

I've done the rename, but I'll also make sure you have permissions for the future.