Merge branch 'wc/find-commit-with-pattern-on-detached-head'

Merge branch 'wc/find-commit-with-pattern-on-detached-head'

"git rev-parse ':/substring'" did not consider the history leading
only to HEAD when looking for a commit with the given substring,
when the HEAD is detached.  This has been fixed.

* wc/find-commit-with-pattern-on-detached-head:
  sha1-name.c: for ":/", find detached HEAD commits