diff --git a/modules/git/git_branch_cleanup.md b/modules/git/git_branch_cleanup.md
index 26d70623..f0c91619 100644
--- a/modules/git/git_branch_cleanup.md
+++ b/modules/git/git_branch_cleanup.md
@@ -1,3 +1,22 @@
 # Git branch cleanup
 
-Remove any local git branch no longer being tracked in origin / remote repo.
+Remove any local git branches that have been merged and optionally remove any
+remote branches that have been merged.
+
+Load with:
+```nushell
+source modules/git/git_branch_cleanup.nu
+```
+
+To remove merged branches:
+```nushell
+git branch-cleanup
+```
+
+To keep merged branches that start with "releases/":
+
+```nushell
+git config --local --add branch-cleanup.keep 'releases/.*'
+```
+
+Keep branch patterns are space-separated
diff --git a/modules/git/git_branch_cleanup.nu b/modules/git/git_branch_cleanup.nu
index 4817bc8b..9dc3967b 100644
--- a/modules/git/git_branch_cleanup.nu
+++ b/modules/git/git_branch_cleanup.nu
@@ -1,4 +1,171 @@
-#!/usr/bin/env nu
+# Adapted from original by Yorick Sijsling
+#
+# Adapted from bash version `git cleanup-repo` by Rob Miller <rob@bigfish.co.uk>
+# https://gist.github.com/robmiller/5133264
 
+# Delete local (and optionally remote) merged branches
+#
+# Set branch-cleanup.keep locally to a space-separated list of branch patterns to keep
+export def "git branch-cleanup" [
+  upstream: string@remotes = "origin" # Upstream remote repository
+] {
+  let current_branch = current_branch
+  let default_branch = get_default_branch $"refs/remotes/($upstream)/HEAD"
+  let keep = get_keep
 
-git branch -vl | lines | split column " " BranchName Hash Status --collapse-empty | where Status == '[gone]' | each { |it| git branch -D $it.BranchName }
+  # Switch to the default branch
+  switch_branch $default_branch
+
+  # Make sure we're working with the most up-to-date version of the default
+  # branch.
+  run-external "git" "fetch"
+
+  # Prune obsolete remote tracking branches. These are branches that we
+  # once tracked, but have since been deleted on the remote.
+  run-external "git" "remote" "prune" $upstream
+
+  # Delete local branches that have been fully merged into the default branch
+  list_merged $upstream $default_branch $keep
+  | each {|branch|
+    delete_local $branch
+  }
+
+  # Again with remote branches
+  let merged_on_remote = list_merged --remote $upstream $default_branch $keep
+
+  if not ( $merged_on_remote | is-empty ) {
+    print "The following remote branches are fully merged and will be removed:"
+
+    $merged_on_remote
+    | each {||
+      print $"\t($in)"
+    }
+
+    print ""
+
+    if ( input --suppress-output "Continue (y/N)? " | str trim ) == "y" {
+      $merged_on_remote
+      | each {|branch|
+        delete_remote $upstream $branch
+      }
+    }
+  }
+
+  switch_branch $current_branch
+}
+
+# The current branch name
+def current_branch [] {
+  run-external --redirect-stdout "git" "branch" "--show-current"
+  | into string
+  | str trim
+}
+
+# Delete a local branch
+def delete_local [
+  branch: string # Branch to delete
+] {
+ run-external "git" "branch" "--delete" $branch
+}
+
+# Delete a remote branch
+def delete_remote [
+  upstream: string # Repository to delete from
+  branch: string   # branch to delete
+] {
+  run-external "git" "push" "--quiet" "--delete" $upstream $branch
+}
+
+# Get the default branch
+def get_default_branch [
+  upstream: string # Repository to get the upstream branch name from
+] {
+  let args = [
+    "--short"
+    $upstream
+  ]
+
+  run-external --redirect-stdout "git" "symbolic-ref" $args
+  | str trim
+  | path basename
+}
+
+# Get the local set of branches to always keep
+def get_keep [] {
+  let keep = run-external --redirect-stdout "git" "config" "--local" "--get" "branch-cleanup.keep"
+
+  if ( $keep | is-empty ) {
+    return []
+  }
+
+  $keep
+  | str trim
+  | split column " "
+  | get column1
+}
+
+# List all the branches that have been merged fully into the default branch.
+#
+# We use the remote default branch here, just in case our local default branch is out of date.
+def list_merged [
+  --remote # List remote branches (local default)
+  upstream: string   # Upstream repository
+  branch: string     # Default branch
+  keep: list<string> # Patterns to keep. The default branch and HEAD will be added
+] {
+  mut args = [
+    "--list"
+    "--merged" $"($upstream)/($branch)"
+  ]
+
+  if $remote {
+    $args = ( $args | append [
+      "--format" "%(refname:lstrip=3)"
+      "--remote"
+    ])
+  } else {
+    $args = ( $args | append [
+      "--format" "%(refname:lstrip=2)"
+    ])
+  }
+
+  let args = $args
+
+  let keep = (
+    $keep
+    | append [
+      "HEAD",
+      $branch,
+    ]
+  )
+
+  run-external --redirect-stdout "git" "branch" $args
+  | lines
+  | filter {|branch|
+      $keep
+      | all {|pattern|
+        $branch !~ $'\A($pattern)\z'
+      }
+  }
+}
+
+def remotes [] {
+  run-external --redirect-stdout "git" "remote" "-v"
+  | parse "{value}\t{description} ({operation})"
+  | select value description
+  | uniq
+  | sort
+}
+
+# Switch to a different branch
+def switch_branch [
+  branch: string
+] {
+  let args = [
+    "--quiet"
+    "--no-guess"
+    $branch
+  ]
+
+  run-external "git" "switch" $args
+}