[PATCH 0/3] add travis job for linux with musl libc

Recently, we've un-broken git for Linux with musl libc, and we have a serie to fix false negative with busybox shell utils.

There is a sample travis build for this serie applied on top of master: https://travis-ci.org/github/sgn/git/builds/667111988

And, after merging with my v4 to fix busybox false negative: https://travis-ci.org/github/sgn/git/builds/667112197

Đoàn Trần Công Danh (3):
  ci: libify logic for usage and checking CI_USER
  ci: refactor docker runner script
  travis: build and test on Linux with musl libc and busybox

 .travis.yml                                 | 10 +++++-
 azure-pipelines.yml                         |  4 +--
 ci/lib-docker.sh                            | 37 +++++++++++++++++++++
 ci/run-alpine-build.sh                      | 31 +++++++++++++++++
 ci/{run-linux32-docker.sh => run-docker.sh} | 20 +++++++----
 ci/run-linux32-build.sh                     | 35 +------------------
 6 files changed, 94 insertions(+), 43 deletions(-)
 create mode 100644 ci/lib-docker.sh
 create mode 100755 ci/run-alpine-build.sh
 rename ci/{run-linux32-docker.sh => run-docker.sh} (46%)