Update CHANGELOG and PROJECTS with the tree cache changes

CHANGELOG.md

@@ -13,6 +13,9 @@ v0.21 + 1
   us to safely update a reflog with arbitrary contents, as we need to
   do for stash.
 
+* The index' tree cache is now filled upon read-tree and write-tree
+  and the cache is written to disk.
+
 * LF -> CRLF filter refuses to handle mixed-EOL files
 
 * LF -> CRLF filter now runs when * text = auto (with Git for Windows 1.9.4)

PROJECTS.md

@@ -88,8 +88,6 @@ might make good smaller projects by themselves.
 * Upgrade internal libxdiff code to latest from core Git
 * Improve index internals with hashtable lookup for files instead of
   using binary search every time
-* Make the index write the cache out to disk (with tests to gain
-  confidence that the caching invalidation works correctly)
 * Tree builder improvements:
     * Use a hash table when building instead of a list
     * Extend to allow building a tree hierarchy