feat: add git-delete-gone-branches command

Adds a new command to delete local branches whose remote-tracking
branch has been deleted (shown as [gone] in git branch -vv).

This is a common need after PRs are merged and remote branches are
cleaned up, leaving stale local branches behind.

Features:
- Deletes all local branches with a gone remote in one command
- --dry-run / -n flag to preview branches before deletion

Closes #1220

Commands.md

@@ -18,6 +18,7 @@
  - [`git cp`](#git-cp)
  - [`git create-branch`](#git-create-branch)
  - [`git delete-branch`](#git-delete-branch)
+ - [`git delete-gone-branches`](#git-delete-gone-branches)
  - [`git delete-merged-branches`](#git-delete-merged-branches)
  - [`git delete-squashed-branches`](#git-delete-squashed-branches)
  - [`git delete-submodule`](#git-delete-submodule)
@@ -932,6 +933,21 @@ Delete local and remote tag `name`:
 $ git delete-tag 0.0.1
 ```
 
+## git delete-gone-branches
+
+Deletes all local branches whose remote-tracking branch has been deleted (i.e. branches shown as `[gone]` in `git branch -vv`). Use `--dry-run` to preview what would be deleted.
+
+```bash
+$ git delete-gone-branches
+Deleted branch feature-123 (was abc1234).
+Deleted branch feature-456 (was def5678).
+
+$ git delete-gone-branches --dry-run
+Would delete the following branches:
+  feature-123
+  feature-456
+```
+
 ## git delete-merged-branches
 
 Deletes branches that are listed in `git branch --merged`.

bin/git-delete-gone-branches

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+dry_run=false
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    -n|--dry-run)
+      dry_run=true
+      shift
+      ;;
+    *)
+      echo "Unknown option: $1"
+      echo "Usage: git delete-gone-branches [-n|--dry-run]"
+      exit 1
+      ;;
+  esac
+done
+
+gone_branches=$(git branch -vv | awk '/: gone\]/{print $1}')
+
+if [ -z "$gone_branches" ]; then
+  echo "No branches with a gone remote found."
+  exit 0
+fi
+
+if [ "$dry_run" = true ]; then
+  echo "Would delete the following branches:"
+  echo "$gone_branches"
+  exit 0
+fi
+
+echo "$gone_branches" | xargs git branch -D

etc/git-extras-completion.zsh

@@ -213,6 +213,11 @@ _git-delete-branch() {
     __gitex_branch_names_unique
 }
 
+_git-delete-gone-branches() {
+    _arguments \
+        '(-n --dry-run)'{-n,--dry-run}'[show branches that would be deleted without deleting]'
+}
+
 _git-delete-squashed-branches() {
     _arguments \
         ':branch-name:__gitex_branch_names'
@@ -421,6 +426,7 @@ zstyle ':completion:*:*:git:*' user-commands $existing_user_commands \
     count:'show commit count' \
     create-branch:'create branches' \
     delete-branch:'delete branches' \
+    delete-gone-branches:'delete branches whose remote is gone' \
     delete-merged-branches:'delete merged branches' \
     delete-squashed-branches:'delete squashed branches' \
     delete-submodule:'delete submodules' \

man/git-delete-gone-branches.md

@@ -0,0 +1,36 @@
+git-delete-gone-branches(1) -- Delete branches whose remote is gone
+====================================================================
+
+## SYNOPSIS
+
+`git-delete-gone-branches` [-n|--dry-run]
+
+## DESCRIPTION
+
+  Deletes all local branches whose remote-tracking branch has been deleted
+  (i.e. branches marked as `[gone]` in `git branch -vv`). This commonly
+  happens after a pull request is merged and the remote branch is removed.
+
+## OPTIONS
+
+  -n, --dry-run
+
+  Show the branches that would be deleted without actually deleting them.
+
+## EXAMPLES
+
+    $ git delete-gone-branches
+
+    $ git delete-gone-branches --dry-run
+
+## AUTHOR
+
+Written by Utsav Sabharwal &lt;<utsav.sabharwal@sysdig.com>&gt;
+
+## REPORTING BUGS
+
+&lt;<https://github.com/tj/git-extras/issues>&gt;
+
+## SEE ALSO
+
+&lt;<https://github.com/tj/git-extras>&gt;