feat: Add option to turn off setup of shell completion (#342)

### Issue
- When I moved from Linux => Mac I didn't have bash completion package
installed and so got these errors (plus turns out I really prefer to
complete on filenames even though the branch complete is a nice feature)

Screenshot of errors I see:
![Screenshot 2024-12-11 at 1 32
14 PM](https://github.com/user-attachments/assets/56e4d8b4-cb00-481e-9e4b-2c1723a4f45f)

### Proposed Fix
- Add an option `git_skip_shell_completion` that is backward compatible
and will ignore any shell completion setup

git.scmbrc.example

@@ -14,6 +14,8 @@ export ga_auto_remove="yes"
 #   Note: Bash tab completion will not be automatically set up for your aliases if you disable this option.
 export git_setup_aliases="yes"
 
+# - Set the following option to 'yes' if you want to turn off shell completion setup
+# export git_skip_shell_completion="yes" 
 
 # Git Index Config
 # ----------------------------------------------

lib/git/aliases.sh

@@ -75,9 +75,11 @@ __git_alias () {
     fi
 
     alias $alias_str="$cmd_prefix $cmd${cmd_args:+ }${cmd_args[*]}"
-    if [ "$shell" = "bash" ]; then
-      __define_git_completion "$alias_str" "$cmd"
-      complete -o default -o nospace -F _git_"$alias_str"_shortcut "$alias_str"
+    if [ "$git_skip_shell_completion" != "yes" ]; then
+      if [ "$shell" = "bash" ]; then
+        __define_git_completion "$alias_str" "$cmd"
+        complete -o default -o nospace -F _git_"$alias_str"_shortcut "$alias_str"
+      fi
     fi
   fi
 }
@@ -180,17 +182,19 @@ fi
 
 
 # Tab completion
-if [ $shell = "bash" ]; then
-  # Fix to preload Arch bash completion for git
-  [[ -s "/usr/share/git/completion/git-completion.bash" ]] && source "/usr/share/git/completion/git-completion.bash"
-  # new path in Ubuntu 13.04
-  [[ -s "/usr/share/bash-completion/completions/git" ]] && source "/usr/share/bash-completion/completions/git"
-  complete -o default -o nospace -F __git_wrap__git_main $git_alias
-
-  # Git repo management & aliases.
-  # If you know how to rewrite _git_index_tab_completion() for zsh, please send me a pull request!
-  complete -o nospace -F _git_index_tab_completion git_index
-  complete -o nospace -F _git_index_tab_completion $git_index_alias
-else
-  compdef _git_index_tab_completion git_index $git_index_alias
+if [ "$git_skip_shell_completion" != "yes" ]; then
+  if [ $shell = "bash" ]; then
+    # Fix to preload Arch bash completion for git
+    [[ -s "/usr/share/git/completion/git-completion.bash" ]] && source "/usr/share/git/completion/git-completion.bash"
+    # new path in Ubuntu 13.04
+    [[ -s "/usr/share/bash-completion/completions/git" ]] && source "/usr/share/bash-completion/completions/git"
+    complete -o default -o nospace -F __git_wrap__git_main $git_alias
+
+    # Git repo management & aliases.
+    # If you know how to rewrite _git_index_tab_completion() for zsh, please send me a pull request!
+    complete -o nospace -F _git_index_tab_completion git_index
+    complete -o nospace -F _git_index_tab_completion $git_index_alias
+  else
+    compdef _git_index_tab_completion git_index $git_index_alias
+  fi
 fi

lib/git/branch_shortcuts.sh

@@ -47,9 +47,11 @@ __git_alias "$git_branch_delete_alias"       "_scmb_git_branch_shortcuts" "-d"
 __git_alias "$git_branch_delete_force_alias" "_scmb_git_branch_shortcuts" "-D"
 
 # Define completions for git branch shortcuts
-if [ "$shell" = "bash" ]; then
-  for alias_str in $git_branch_alias $git_branch_all_alias $git_branch_move_alias $git_branch_delete_alias; do
-    __define_git_completion $alias_str branch
-    complete -o default -o nospace -F _git_"$alias_str"_shortcut $alias_str
-  done
+if [ "$git_skip_shell_completion" != "yes" ]; then
+  if [ "$shell" = "bash" ]; then
+    for alias_str in $git_branch_alias $git_branch_all_alias $git_branch_move_alias $git_branch_delete_alias; do
+      __define_git_completion $alias_str branch
+      complete -o default -o nospace -F _git_"$alias_str"_shortcut $alias_str
+    done
+  fi
 fi

lib/git/tools.sh

@@ -122,8 +122,10 @@ git_swap_remotes() {
   echo "Swapped $1 <-> $2"
 }
 # (use git fetch tab completion)
-if [ "$shell" = "bash" ]; then
-  complete -o default -o nospace -F _git_fetch git_swap_remotes
+if [ "$git_skip_shell_completion" != "yes" ]; then
+  if [ "$shell" = "bash" ]; then
+    complete -o default -o nospace -F _git_fetch git_swap_remotes
+  fi
 fi