CompareUpstreams: support comparing against snapshots.

CompareUpstreams used to compare ojluni sources vs. copies of
the upstream sources stored in a "Repository" (checked-out
and built source repositories).

Since I've not recently been able to build OpenJDK 8 (requires
an older C++ compiler than what is installed on my machine),
I couldn't run CompareUpstreams without losing the information
for the files that are only generated during the OpenJDK 8 build.

This CL changes CompareUpstreams to instead compare against the
snapshot of only the files of interest from the upstream
repository (which in turn is a copy of a historic output of
CopyUpstreamFiles at a time when I still had a compiled version
of OpenJDK 8 on my local disk).

The old functionality is still available/present in the code,
but it's turned off by a hard-coded boolean constant for now.

Note that the CompareUpstreams tool still requires the environment
variable OPENJDK_HOME (which points to a directory with checked-out
upstream repositories) to be set, but the files in those directories
are not looked at unless the aforementioned hard-coded boolean
constant is changed; I didn't bother refactoring that part for now.

Test: Re-generated the verification spreadsheet and checked
      that the latest version as well as the changes relative
      to the previous version look sane and doesn't lose the
      comparison information for generated files.

Change-Id: Ibde72b898c48ad2a29456e2af8b54708696c9bf3

0 files changed, 0 insertions, 0 deletions