Change main branch from "master" to "main"

[willschlitzer]

In the interest of inclusivity, should we change the main git branch from master to main? This would be in line with changes to large Python repos, including CPython, Numpy, Flask, and Django, as well as the default main branch for all new GitHub repos.

Are you willing to help implement and maintain this feature? Yes

[seisman]

I'm OK with the change.

[michaelgrund]

Mee, too! Are there any technical issues which could come up when changing the master branch?

[core-man]

Mee, too! Are there any technical issues which could come up when changing the master branch?

I don't think so from my experience for this change 😄

[weiji14]

Guidance is at https://github.com/github/renaming. Contributors will need to point their git remote to the new 'main' branch locally on their computers, and there will need to be a Pull Request to rename 'master' to 'main' across our documentation/CI scripts/etc.

[maxrjones]

I support the change. Seems that github has made the process rather streamlined.

[willschlitzer]

Guidance is at https://github.com/github/renaming. Contributors will need to point their git remote to the new 'main' branch locally on their computers, and there will need to be a Pull Request to rename 'master' to 'main' across our documentation/CI scripts/etc.

I don't have the rights to rename the default branch, but I have submitted a draft PR changing documentation and CI scripts.

[maxrjones]

At the same time, we could update the 'master' CPT references in the docstrings for these two functions:

./pygmt/src/grd2cpt.py
./pygmt/src/makecpt.py

[seisman]

At the same time, we could update the 'master' CPT references in the docstrings for these two functions:

./pygmt/src/grd2cpt.py
./pygmt/src/makecpt.py

But they are called "master" CPT in GMT.

[seisman]

One more note: there are some links in the old documentation that are linked to files on the master branch, for examples, links to the LICENSE.txt, CONTRIBUTING.md and links to example source files. Changing "master" to "main" also breaks the old documentation (including the latest v0.4.0 documentation).

Does GitHub automatically redirect any links of master branch to "main"? If not, do we want to update the old documentation in the gh-pages?