feat(hooks): add pr#36 automate pre-commit hook

Initial feature addition of automating pre-commit hooks installation if
present for git-flow cjs. This is the actual pull request that was
subbmited by [PauloASilva]([email protected])

Closes #36

git-flow-init

@@ -429,6 +429,28 @@ file=    use given config file
 		git_do config $gitflow_config_option gitflow.path.hooks "$hooks_dir"
 	fi
 
+	# Automate pre-commit hook install if it exists on git-flow hooks directory
+    hooks_dir=$(git config --get gitflow.path.hooks)
+    hooks_dir=${hooks_dir%%/}
+    if [ -f "$hooks_dir/pre-commit" ]; then
+        DOT_GIT_DIR=$(git rev-parse --git-dir)
+        LOCAL_GIT_HOOKS_DIR="$DOT_GIT_DIR/hooks"
+        # Check whether there's a previous local pre-commit hook to backup
+        if [ -f "$LOCAL_GIT_HOOKS_DIR/pre-commit" ]; then
+            backup="(local hook will be saved)"
+        fi
+        default_suggestion="Y"
+        printf "Install pre-commit hook%s? [$default_suggestion] " " $backup"
+        if noflag defaults; then
+            read answer
+        else
+            printf "\n"
+        fi
+        if [ "${answer:-$default_suggestion}" = "Y" ]; then
+            ln -s "$hooks_dir/pre-commit" -t "$LOCAL_GIT_HOOKS_DIR" --backup
+        fi
+    fi
+
 	# TODO: what to do with origin?
 }