This extracts the overlay context and archive parsing from guru into
buildutil.
At least one tool (gogetdoc) has a vendored copy of this code already,
and more tools implementing the same functionality will follow.
The new code in buildutil is an almost identical copy of the code in
guru (names aside), except for the following changes:
- Instead of reading into a bytes.Buffer, we read directly into a []byte
of appropriate size
- sameFile first attempts a simple comparison of path.Clean'ed paths.
Change-Id: I97cd978ccc10722e3648e5e10625fa7f1407f202
Reviewed-on: https://go-review.googlesource.com/21805
Reviewed-by: Alan Donovan <adonovan@google.com>
446a18e709