gitlab-backup: don't keep backup_gitlab.pulled files

add option to remove or keep pulled backup data

[ kirr: The .pulled files with gitlab backup data (SQL and the like)
  were originally not removed "just in case" in the early days of
  git/gitlab-backup. They are clearly not needed to be kept since their
  content is entered into git backup database by gitlab-backup, and
  leaving those .pulled files just wastes disk space.

  So default to not keep them around and for now add an option to
  forcibly preserve the raw gitlab backup if we'll need it just in case or
  for the debugging.

  However if it turns out we won't really need -keep in practice, it
  might go away in some time. ]

/reviewed-on !3

contrib/gitlab-backup

@@ -104,6 +104,7 @@ need_gitlab_config() {
 
 # pull gitlab data into git-backup repository
 backup_pull() {
+    keep_pulled_backup=$1
     need_gitlab_config
 
     # 1. dump all gitlab data except repositories & db
@@ -210,8 +211,13 @@ backup_pull() {
     echo " * git-backup pull everything"
     $GIT_BACKUP pull "$tmpd/gitlab_backup:gitlab/misc"  $GITLAB_REPOS_PATH:gitlab/repo
 
-    # mark backup_tar as pulled and cleanup
-    mv "$backup_tar" "$backup_tar.pulled"
+    if [ "$keep_pulled_backup" == "n" ]; then
+        # remove pulled as they are not needed
+        rm -f "$backup_tar"
+    else
+        # mark backup_tar as pulled and cleanup
+        mv "$backup_tar" "$backup_tar.pulled"
+    fi
     rm -rf "$tmpd"
 
     echo OK
@@ -387,7 +393,7 @@ umask 0077    # XXX maybe not good - e.g. git-data/repositories should (?) be rw
 
 
 usage() {
-    echo "Usage: gitlab-backup [pull | restore (-vupok, -go) <commit-ish>]"
+    echo "Usage: gitlab-backup [pull (-keep) | restore (-vupok, -go) <commit-ish>]"
 }
 
 
@@ -397,7 +403,23 @@ shift
 
 case "$action" in
     pull)
-        backup_pull
+        keep=n      # keep pulled gitlab backup data
+        while test $# != 0; do
+            case "$1" in
+            -keep)
+                keep=y
+                ;;
+            -*)
+                die `usage`
+                ;;
+            *)
+                break
+                ;;
+            esac
+            shift
+        done
+
+        backup_pull $keep
         ;;
     restore)
         vupok=n     # gitlab version >= backup's gitlab version is ok