Batch changing default branch for multiple repos

Using /x1/gitbox/bin/change-default-branch.py on gitbox (as root or www-data), you can batch change multiple repos default branch.

Repo names can include .git or not, it doesn't matter.

Usage examples:

• Changing all repos from master to main:

  $ /x1/gitbox/bin/change-default-branch.py main
  foo.git
  bar.git
  baz.git
  (Ctrl+D)

• Changing repos to various branches, but default to main if not specified

  $ /x1/gitbox/bin/change-default-branch.py main
  foo.git
  bar.git blurbbranch
  baz.git anotherbranch
  (Ctrl+D)

• Alternately, changing all repos to main by reading from a text list:

  $ /x1/gitbox/bin/change-default-branch.py main < list-of-repos.txt