Fix key encoding to be null terminated

Fix key encoding to be null terminated

This will allow the use of automatic indicies to fulfil basic ancestor queries.
Otherwise keys with many components sort after keys with few components (instead
of lexicographically per token)

R=dnj@google.com, tandrii@chromium.org, dnj@chromium.org, estaab@chromium.org, vadimsh@chromium.org
BUG=

Committed: https://github.com/luci/gae/commit/7c292a416ca39a3232cc5d46fe82c3f1a16f1c6a

[tandrii(chromium), 2015-08-15 18:54:36]

lgtm

[dnj (Google), 2015-08-15 19:06:55]

dnj@google.com changed reviewers:
+ dnj@google.com

[dnj (Google), 2015-08-15 19:06:55]

lgtm w/ nit

https://codereview.chromium.org/1286093007/diff/1/service/datastore/serialize...
File service/datastore/serialize/serialize.go (right):

https://codereview.chromium.org/1286093007/diff/1/service/datastore/serialize...
service/datastore/serialize/serialize.go:107: if len(toks)+1 >=
ReadKeyNumToksReasonableLimit {
nit: Why greater-than-or-equal and not greater-than?

If I say, "your limit is 10 cookies", you would expect to be able to eat 10
cookies, not 9 :)

[iannucci, 2015-08-15 21:56:13]

On 2015/08/15 19:06:55, dnj (Google) wrote:
> lgtm w/ nit
> 
>
https://codereview.chromium.org/1286093007/diff/1/service/datastore/serialize...
> File service/datastore/serialize/serialize.go (right):
> 
>
https://codereview.chromium.org/1286093007/diff/1/service/datastore/serialize...
> service/datastore/serialize/serialize.go:107: if len(toks)+1 >=
> ReadKeyNumToksReasonableLimit {
> nit: Why greater-than-or-equal and not greater-than?
> 
> If I say, "your limit is 10 cookies", you would expect to be able to eat 10
> cookies, not 9 :)

Ah oops... fixed.

[iannucci, 2015-08-15 21:57:06]

Committed patchset #2 (id:20001) manually as
7c292a416ca39a3232cc5d46fe82c3f1a16f1c6a (presubmit successful).