tree 5fcd7e537134e4902cd23953d191cad875fc0951
parent 4d3aa4ea23549c021b8b16e21c494fa5c12f87fb
author Michael Bolin <mbolin@fb.com> 1379717517 -0700
committer Michael Bolin <mbolin@fb.com> 1380132711 -0700

Compute the RuleKey with and without deps simultaneously.

Summary:
It turns out that a `Hasher` created via `Hashing.sha1()` can have
its `hash()` method invoked only once. Therefore, to compute both
RuleKeys simultaneously, this diff introduces an AppendingHasher
that makes it possible to build up the SHA1 digest for a RuleKey
without deps, get its hash, and then update the digest with the deps
info, and get its hash again.

Test Plan:
Created a comprehensive unit test, AppendingHasherTest.
The updates to AbstractCachingBuildRuleTest.java reflect the
changes to RuleKey.