ARROW-5011: [Release] Add support in source release script for custom git hash
ARROW-5011: [Release] Add support in source release script for custom git hash

This is a minor feature to help debugging said script on a by overriding
the git-archive hash instead of the hash inferred from the release tag.

Author: François Saint-Jacques <fsaintjacques@gmail.com>

Closes #4032 from fsaintjacques/ARROW-5011-release-source-hash and squashes the following commits:

e43f4286d <François Saint-Jacques> ARROW-5011:  Add support in source release script for custom hash

laurentgo/arrow,icexelloss/arrow,icexelloss/arrow,laurentgo/arrow,apache/arrow,apache/arrow,cpcloud/arrow,apache/arrow,cpcloud/arrow,icexelloss/arrow,wesm/arrow,xhochy/arrow,cpcloud/arrow,laurentgo/arrow,icexelloss/arrow,cpcloud/arrow,renesugar/arrow,apache/arrow,xhochy/arrow,apache/arrow,wesm/arrow,xhochy/arrow,renesugar/arrow,majetideepak/arrow,xhochy/arrow,renesugar/arrow,renesugar/arrow,kou/arrow,icexelloss/arrow,xhochy/arrow,kou/arrow,laurentgo/arrow,wesm/arrow,majetideepak/arrow,cpcloud/arrow,icexelloss/arrow,cpcloud/arrow,renesugar/arrow,kou/arrow,majetideepak/arrow,majetideepak/arrow,kou/arrow,renesugar/arrow,icexelloss/arrow,cpcloud/arrow,icexelloss/arrow,laurentgo/arrow,laurentgo/arrow,kou/arrow,majetideepak/arrow,kou/arrow,xhochy/arrow,wesm/arrow,xhochy/arrow,majetideepak/arrow,cpcloud/arrow,wesm/arrow,renesugar/arrow,xhochy/arrow,xhochy/arrow,majetideepak/arrow,laurentgo/arrow,majetideepak/arrow,majetideepak/arrow,apache/arrow,xhochy/arrow,xhochy/arrow,renesugar/arrow,renesugar/arrow,apache/arrow,wesm/arrow,laurentgo/arrow,laurentgo/arrow,apache/arrow,icexelloss/arrow,wesm/arrow,wesm/arrow,icexelloss/arrow,cpcloud/arrow,cpcloud/arrow,cpcloud/arrow,kou/arrow,laurentgo/arrow,apache/arrow,wesm/arrow,kou/arrow,renesugar/arrow,cpcloud/arrow,laurentgo/arrow,apache/arrow,renesugar/arrow,apache/arrow,majetideepak/arrow,renesugar/arrow,wesm/arrow,icexelloss/arrow,majetideepak/arrow,icexelloss/arrow,apache/arrow,wesm/arrow,majetideepak/arrow,kou/arrow,xhochy/arrow,xhochy/arrow,icexelloss/arrow,kou/arrow,laurentgo/arrow,renesugar/arrow,xhochy/arrow,renesugar/arrow,kou/arrow,wesm/arrow,cpcloud/arrow,icexelloss/arrow,renesugar/arrow,kou/arrow,wesm/arrow,wesm/arrow,laurentgo/arrow,kou/arrow,kou/arrow,apache/arrow,apache/arrow,cpcloud/arrow,majetideepak/arrow,majetideepak/arrow,laurentgo/arrow,majetideepak/arrow,xhochy/arrow,laurentgo/arrow