Merge branch 'du/get-tar-commit-id-is-plumbing' into maint

Doc update to mark "git get-tar-commit-id" as a plumbing command.

* du/get-tar-commit-id-is-plumbing:
  doc: move git-get-tar-commit-id to plumbing

Author: gitster

command-list.txt

@@ -96,7 +96,7 @@ git-for-each-ref                        plumbinginterrogators
 git-format-patch                        mainporcelain
 git-fsck                                ancillaryinterrogators          complete
 git-gc                                  mainporcelain
-git-get-tar-commit-id                   ancillaryinterrogators
+git-get-tar-commit-id                   plumbinginterrogators
 git-grep                                mainporcelain           info
 git-gui                                 mainporcelain
 git-hash-object                         plumbingmanipulators