Merge branch 'sb/test-helper-excludes'

Simplify the ignore rules for t/helper directory.

* sb/test-helper-excludes:
  t/helper: ignore everything but sources

t/helper/.gitignore

-/test-chmtime
-/test-ctype
-/test-config
-/test-date
-/test-delta
-/test-drop-caches
-/test-dump-cache-tree
-/test-dump-fsmonitor
-/test-dump-split-index
-/test-dump-untracked-cache
-/test-example-decorate
-/test-fake-ssh
-/test-scrap-cache-tree
-/test-genrandom
-/test-hashmap
-/test-index-version
-/test-lazy-init-name-hash
-/test-line-buffer
-/test-match-trees
-/test-mergesort
-/test-mktemp
-/test-online-cpus
-/test-parse-options
-/test-path-utils
-/test-prio-queue
-/test-read-cache
-/test-ref-store
-/test-regex
-/test-revision-walking
-/test-run-command
-/test-sha1
-/test-sha1-array
-/test-sigchain
-/test-strcmp-offset
-/test-string-list
-/test-submodule-config
-/test-subprocess
-/test-svn-fe
-/test-urlmatch-normalization
-/test-wildmatch
-/test-write-cache
+*
+!*.sh
+!*.[ch]
+!*.gitignore
+