update default defaultBranch to main

[ahvigil]

New feature

The last few years have seen many projects move from master to main as the default project branch. Notably github and gitlab now use main as the default branch for new repos. Sensitive issues of historical and cultural significance aside, does it make sense to update the default branch name in nextflow to reflect this updated and commonly used convention? This is now the default on 2 of the 3 cloud version control providers mentioned in the documentation for the manifest scope (and github is arguably the largest and most influential of these).

On the other hand, I believe the default behavior of git itself is to continue using master for newly created repos unless configured otherwise via init.defaultBranch, and as far as I know bitbucket still uses that convention as well (though both have added the ability to override that). I could see the default behavior of git init as a compelling reason to maintain the current nextflow manifest default.

Usage scenario

This may be mostly a cosmetic issue as I'm not entirely sure what the manifest defaultBranch gets used for?

Suggest implementation

update the constant at

nextflow/modules/nf-commons/src/main/nextflow/Const.groovy

Line 145 in 1daebee

static public final String DEFAULT_BRANCH = 'master'

along with various references to master in tests and function defaults.

[ahvigil]

looks like #1670 is related

[bentsherman]

Duplicate of #3593, in the other issue I suggested that Nextflow accept both master and main as default branches