The Git Travis CI OSX build always installs the latest versions of Git LFS and
Perforce via brew and the Linux build installs fixed versions. Consequently new
LFS/Perforce versions can break the OS X build even if there is no change in
Git.
Signed-off-by: NLars Schneider <larsxschneider@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Signed-off-by: NLars Schneider <larsxschneider@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

We assume Git developers have a reasonably modern compiler and recommend
them to enable the DEVELOPER makefile knob to ensure their patches are
clear of all compiler warnings the Git core project cares about.

Enable the DEVELOPER makefile knob in the Travis-CI build.
Suggested-by: NJeff King <peff@peff.net>
Signed-off-by: NLars Schneider <larsxschneider@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Set `sudo: false` to explicitly use the (faster) container-based
infrastructure for the Travis-CI Linux build.

More info:
https://docs.travis-ci.com/user/ci-environment/#Virtualization-environmentsSigned-off-by: NLars Schneider <larsxschneider@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The Travis-CI machines are in a clean state in the beginning of every run
(transient by default). Use the Travis-CI cache feature to make the prove
state persistent across consecutive Travis-CI runs on the same branch.
This allows to run previously failed tests first and run remaining tests
in slowest to fastest order. As a result it is less likely that Travis-CI
needs to wait for a single test at the end which speeds up the test suite
execution by ~2 min.

Travis-CI can only cache entire directories. Prove stores the .prove file
always in the t/ directory but we don't want to cache the entire t/ directory.
Therefore we create a symlink from $HOME/travis-cache/.prove to t/.prove and
cache the $HOME/travis-cache directory.

Unfortunately the cache feature is only available (for free) on the
Travis-CI Linux environment.
Suggested-by: NJeff King <peff@peff.net>
Signed-off-by: NLars Schneider <larsxschneider@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The tests are currently executed on "Ubuntu 12.04 LTS Server Edition
64 bit" and on "OS X Mavericks" using gcc and clang.

Perforce and Git-LFS are installed and therefore available for the
respective tests.
Signed-off-by: NLars Schneider <larsxschneider@gmail.com>
Signed-off-by: NJeff King <peff@peff.net>