Check that jar output is byte-for-byte identical

[johnynek]

This is to address #53

This adds a jar creator that is a minor edit of:
https://github.com/bazelbuild/bazel/blob/master/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/jarhelper/JarCreator.java

to remove the unneeded guava dependency (so it would build easier), which sets the timestamps to fixed values, which makes the jars pure functions of the contents.

[johnynek]

this seems to pass on linux, but it fails on my OSX machine.

[damienmg]

test this please

[bazel-io]

Can one of the admins verify this patch?

[johnynek]

Here is the issue:

http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/sun/tools/jar/Main.java#445

jar seems to hardwire writing the current time. Not sure how linux escapes this.

[johnynek]

http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/8u40-b25/sun/tools/jar/Main.java?av=f#526

[johnynek]

This passes on OSX.

@ianoc @non this is what I came up with.

This is minor edit of:
https://github.com/bazelbuild/bazel/blob/master/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/jarhelper/JarCreator.java

to remove the unneeded guava dependency (so it would build easier).

[johnynek]

this closes #53

[johnynek]

@smparkes @dinowernli review?

This does not change the build time for an internal repo relative to sha: 7b891ad

[smparkes]

Nice. LGTM

[damienmg]

FWIW, @bazel_tools//tools/zip:zipper is a zip implementation that strip out timestamp. Might be easier to refer to it that to fork SingleJar's Jar implementation. (Also faster)

[johnynek]

That is good to know about instead of using system zip, but what about making manifests? Seems nice to reuse that bit?

[damienmg]

Oh I see, then maybe you can use directly the SingleJar binary. Just ask if you need to get rid of the file fork and I can probably help you sort that out.

[dinowernli]

Sorry, out of town ;)

LGTM