chore: Update references to default branch to 'main'

[matthewfeickert]

Description

Join most of the rest of Scikit-HEP and use 'main' as the default branch. This has already been done in GitHub's settings, but this updates all reference to the default branch from 'master' to 'main'. The remaining instances of 'master' in the repo are the following which are fine to keep:

$ git grep "master"
docs/conf.py:# The master toctree document.
docs/conf.py:master_doc = 'index'
docs/conf.py:        master_doc,
docs/conf.py:man_pages = [(master_doc, 'pyhf', 'pyhf Documentation', [author], 1)]
docs/conf.py:        master_doc,
docs/conf.py:# c.f. https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-the-linkcheck-builder
docs/index.rst:.. pyhf documentation master file, created by

We should probably keep the master branch around for a year and occasionally sync it to main just so anyone who relies on master can transition away from it, but we can probably safely delete master from our local machines.

Checklist Before Requesting Reviewer

• Tests are passing
• "WIP" removed from the title of the pull request
• Selected an Assignee for the PR to be responsible for the log summary

Before Merging

For the PR Assignees:

• Summarize commit messages into a comprehensive review of the PR

* Update all references to the default repository branch from 'master' to 'main'.

[codecov]

Codecov Report

Base: 98.29% // Head: 98.29% // No change to project coverage 👍

Coverage data is based on head (aea7dda) compared to base (37abb3b).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2019   +/-   ##
=======================================
  Coverage   98.29%   98.29%           
=======================================
  Files          69       69           
  Lines        4529     4529           
  Branches      738      738           
=======================================
  Hits         4452     4452           
  Misses         45       45           
  Partials       32       32           

Flag	Coverage Δ
contrib	27.51% <ø> (ø)
doctest	61.13% <ø> (ø)
unittests-3.10	96.31% <ø> (ø)
unittests-3.7	96.28% <ø> (ø)
unittests-3.8	96.33% <ø> (ø)
unittests-3.9	96.35% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/pyhf/cli/infer.py	97.61% <ø> (ø)
src/pyhf/cli/spec.py	100.00% <ø> (ø)

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[matthewfeickert]

Relevant RTD build: https://pyhf--2019.org.readthedocs.build/en/2019/

[matthewfeickert]

As this affects the CI workflows this needs to go in next before any other PRs.

[kratsg]

We should probably keep the master branch around for a year and occasionally sync it to main just so anyone who relies on master can transition away from it, but we can probably safely delete master from our local machines.

Just delete it entirely. Nobody's going to be relying on master explicitly unless it's a default thing.

[matthewfeickert]

Just delete it entirely. Nobody's going to be relying on master explicitly unless it's a default thing.

Okay. Just deleted master. 👍