Add support for git worktrees (#353)

Adds numbering & aliasing for branches currently checked out by git
worktrees.

Previously, if you were to create a new git worktree, the branch does
not get picked up with scm_breeze's numbering:
```
$ gco -b tmp && gco - && gco -b tmp2 && gco -
$ git worktree add /tmp/scm_breeze_tmp tmp
$ gb
* [1] main
+ tmp
  [3] tmp2
$ gco 2
error: pathspec '+ tmp' did not match any file(s) known to git
```

With this change, worktrees now appear to the user as "just another
branch." Using scm_breeze aliases, you can swap branches seamlessly,
using numeric aliases and without needing to manually remember & change
directories.

```
$ gb
* [1] main
+ [2] tmp
  [3] tmp2
$ gco 2
Switching to worktree: /tmp/scm_breeze_tmp
```

The `+` distinguishes between branches currently checked out in separate
worktrees

Author: ghthor

lib/git/aliases.sh

@@ -30,7 +30,9 @@ function git(){
   case $1 in
     commit|blame|add|log|rebase|merge|difftool|switch)
       exec_scmb_expand_args "$_git_cmd" "$@";;
-    checkout|diff|rm|reset|restore)
+    checkout)
+      _scmb_git_checkout_shortcuts "${@:2}";;
+    diff|rm|reset|restore)
       exec_scmb_expand_args --relative "$_git_cmd" "$@";;
     branch)
       _scmb_git_branch_shortcuts "${@:2}";;

lib/git/branch_shortcuts.sh

@@ -27,20 +27,54 @@ function _scmb_git_branch_shortcuts {
     line_count = output.lines.to_a.size
     output.lines.each_with_index do |line, i|
       spaces = (line_count > 9 && i < 9 ? "  " : " ")
-      puts line.sub(/^([ *]{2})/, "\\\1\033[2;37m[\033[0m#{i+1}\033[2;37m]\033[0m" << spaces)
+      puts line.sub(/^([ *+]{2})/, "\\\1\033[2;37m[\033[0m#{i+1}\033[2;37m]\033[0m" << spaces)
     end
 EOF
-  )"
+)"
 
   # Set numbered file shortcut in variable
   local e=1 IFS=$'\n'
-  for branch in $($_git_cmd branch "$@" | sed "s/^[* ]\{2\}//"); do
+  for branch in $($_git_cmd branch "$@" | sed "s/^[*+ ]\{2\}//"); do
     export $GIT_ENV_CHAR$e="$branch"
     if [ "${scmbDebug:-}" = "true" ]; then echo "Set \$$GIT_ENV_CHAR$e  => $file"; fi
     let e++
   done
 }
 
+function _scmb_git_checkout_shortcuts {
+  fail_if_not_git_repo || return 1
+
+  if [ -z "$1" ]; then
+    exec_scmb_expand_args $_git_cmd checkout
+    return $?
+  fi
+
+  if [[ "$1" =~ ^[0-9]+$ ]]; then
+    local branch_var="${git_env_char}$1"
+    local branch=$(eval echo "\$$branch_var")
+
+    if [ -n "$branch" ]; then
+      if $_git_cmd worktree list --porcelain 2>/dev/null | grep -q "^branch refs/heads/$branch$"; then
+        local worktree_path=$($_git_cmd worktree list --porcelain | awk "
+          /^worktree / {
+            path = substr(\$0, 10); next
+          }
+          /^branch refs\/heads\/$branch$/ {
+            print path; exit
+          }
+        ")
+        if [ -n "$worktree_path" ] && [ -d "$worktree_path" ]; then
+          echo "Switching to worktree: $worktree_path"
+          cd "$worktree_path"
+          return $?
+        fi
+      fi
+    fi
+  fi
+
+  exec_scmb_expand_args $_git_cmd checkout "$@"
+}
+
 __git_alias "$git_branch_alias"              "_scmb_git_branch_shortcuts" ""
 __git_alias "$git_branch_all_alias"          "_scmb_git_branch_shortcuts" "-a"
 __git_alias "$git_branch_move_alias"         "_scmb_git_branch_shortcuts" "-m"