local-branches-with-missing-remote

#!/usr/bin/env ruby -w

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#
# Begin Commentary
#
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#
# First, if you want to use this, I recommend you change the
# the file mode to executable:
#
#  `chmod +x local-branches-with-missing-remote`
#
# This command writes to STDOUT a list of local branches that
# have upstream tracking branches, but who's upstream branches
# are now gone.
#
# Fair warning, this perhaps follows some of my internalized
# assumptions about repository setup.
#
# I would love if there already existed a function that does
# this, but part of why I write code is to also practice
# algorithms and critical thinking.
#
# Example to list local branches with missing remotes:
#
#  $ cd ~/git/forem ; local-branches-with-missing-remote
#
# Example to delete local branches with missing remotes:
#
#  $ local-branches-with-missing-remote | xargs git remote -D
#
#
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#
# Begin Function
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#
# Prune the remote branches that are gone.  Also, don't worry
# about the output
`git remote update origin --prune >/dev/null 2>&1`

# The remote branch lines are of the form:
#
# - space
# - origin/branch-name
#
# Note: by convention, origin is the upstream I'm concerned
# about
remote_branches = `git branch --remotes`
  .split("\n")
  .map(&:strip)

# The verbose branch lines are of the form:
#
# - Branch Name
# - many spaces
# - SHA of latest commit
# - space
# - OPTIONAL: "[Remote Name]"
# - space
# - Subject of latest commit
local_verbose_branches = `git branch -vv`
  .split("\n")
  .map { |b| b.gsub(/^\*? +/, '').strip }

local_verbose_branches.each do |verbose_branch|
  # Definitely don't want to delete this local branch.
  next if verbose_branch.start_with?("main")

  # Though I no longer use "master" for my projects, there are
  # some outliers that do.
  next if verbose_branch.start_with?("master")

  # I might have a local branch that doesn't have a remote
  # tracking branch.  Skip those
  next unless verbose_branch.include?("[origin")

  branch_name = verbose_branch.split(/ +/)[0]

  # Test if local branch has a remote branch
  next if remote_branches.detect do |rb|
    rb.include?(branch_name)
  end

  # Output the branch name for a local branch with what
  # appears to be a removed upstream branch (e.g., the
  # upstream branch was likely merged and deleted)
  puts branch_name
end